rainwater harvesting reference material

8/9/2019 Rainwater Harvesting Reference Material

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RAINWATER HARVESTINGREFERENCE MATERIAL

SMITH


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Managing Wet Weather with Green Infrastructure

Municipal Handbook

Rainwater Harvesting Policies

prepared by

Christopher Kloss

Low Impact Development Center

The Municipal Handbook is a series of documentsto help local officials implement green infrastructure in their communities.


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Rainwater Harvesting Policies

IntroductionFrom the last half of the 20th century, the U.S. has enjoyed nearly universal access to abundant supplies ofpotable water. But as witnessed by the recent serious and sustained droughts in the Southeast andSouthwest, this past luxury is not something that can be expected for the long term. Future populationgrowth will exert more demand on water systems while climate change is predicted to decrease availablesupplies because of decreased snow pack and drier regional climatic patterns. The U.S. has beenidentified as a country that faces imminent water shortages and a Government Accountability Office(GAO) survey found that water managers in 36 states anticipate water shortages during the first twodecades of this century.1 These challenges will require a more sustainable approach to using water

resources, looking at not only how much water is used, but also the quality of water needed for each use.

The overwhelming majority of the water used in the U.S. comes from freshwater supplies of surface andgroundwater. Water extracted for public systems is treated to potable standards as defined by the SafeDrinking Water Act. Access to high quality water has greatly benefited public health, but it has alsoresulted in our current system that utilizes potable water for virtually every end use, even when lesserquality water would be sufficient. In addition to conservation methods, using alternative sources of waterwill be necessary for more efficient use of water resources.

Rainwater harvesting, collecting rainwater from impervious surfaces and storing it for later use, is atechnique that has been used for millennia. It has not been widely employed in industrialized societiesthat rely primarily on centralized water distribution systems, but with limited water resources andstormwater pollution recognized as serious problems and the emergence of green building, the role thatrainwater harvesting can play for water supply is being reassessed. Rainwater reuse offers a number ofbenefits.2

Provides inexpensive supply of water;

Augments drinking water supplies; Reduces stormwater runoff and pollution;

R d i i b i t


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(UPC) nor International Plumbing Code (IPC) directly address rainwater harvesting in their potable orstormwater sections. Other reuse waters are covered by codes. The UPCs Appendix J addressesreclaimed water use for water closets and urinals and the IPCs Appendix C addresses graywater use forwater closets and urinals along with subsurface irrigation.6 Both sections focus on treatment requirements,measures necessary to prevent cross-contamination with potable water, and appropriate signage andsystem labeling. However, because of a general lack of specific rainwater harvesting guidance somejurisdictions have regulated harvested rainwater as reclaimed water, resulting in more stringentrequirements than necessary. These issues have led to confusion as to what constitutes harvestedrainwater, graywater, or reclaimed water.7

The confusion among waters for reuse and thelack of uniform national guidance has resulted

in differing use and treatment guidelines amongstate and local governments and presents animpediment to rainwater reuse. Texas promotesharvested rainwater for any use includingpotable uses provided appropriate treatment isinstalled; Portland, like many otherjurisdictions, generally recommends rainwateruse to the non-potable applications of irrigation,hose bibbs, water closets, and urinals.

To develop general or national guidance forrainwater harvesting, several factors must beconsidered. While potable use is possible forharvested rainwater, necessary on-site treatmentand perceived public health concerns will likely limit the quantity of rainwater used for potable demands.Irrigation and the non-potable uses of water closets, urinals and HVAC make-up are the end uses that aregenerally the best match for harvested rainwater. A lesser amount of on-site treatment is required for

these uses and, as seen from the use statistics presented above, these uses constitute a significant portionof residential and commercial demand. Focusing harvested rainwater on irrigation and selected non-potable indoor uses can significantly lower demand while allowing a balance and public comfort level

UPC Definitions Waters for Reuse8

Graywater untreated wastewater that has not come in

to contact with black water (sewage). Graywaterincludes used water from bathtubs, showers, lavatories,and water from clothes washing machines.

Reclaimed water water treated to domesticwastewater tertiary standards by a public agencysuitable for a controlled use, including supply to waterclosets, urinals, and trap seal primers for floor drainsand floor sinks. Reclaimed water is conveyed in purplepipes (Californias purple pipe system is one of the

better known water reclamation systems). Harvested rainwater stormwater that is conveyed

from a building roof, stored in a cistern and disinfectedand filtered before being used for toilet flushing. It canalso be used for landscape irrigation.


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Portlands code permits rainwater reuse forpotable uses at family dwellings onlythrough an appeals process. In addition,rainwater used only for outdoor irrigation isnot covered by the code and needs notreatment prior to use. Acceptable indoornon-potable uses are hose bibbs, waterclosets, and urinals. The code illuminatesseveral important issues that need to beconsidered when developing rainwaterharvesting code.

Water quality Water quality andits impact on human health is aprimary concern with rainwaterharvesting. This issue is comprisedof two components: end use of therainwater and treatment provided.Rainwater used for residentialirrigation (on the scale of rainbarrel collection) does not typically

require treatment. Commercialapplications and non-potableindoor uses require treatment butthe type of use will determine theextent of treatment. Eachjurisdiction will need to assess thelevel of treatment with which it iscomfortable, but limiting rainwater

reuse to water closets, urinals andhose bibbs presents little humanhealth risk. Each system will

Excerpts of General RequirementsPortland Rainwater Harvesting Code Guide

General

Harvested rainwater may only be used for waterclosets, urinals, hose bibbs, and irrigation.

Rainwater can only be harvested from roof surfaces.

The first 10 gallons of roof runoff during any rain eventneeds to be diverted away from the cistern to an Officeof Planning & Development Review (OPDR) approvedlocation.

Rainwater Harvesting System Components

Gutters All gutters leading to the cistern require leaf

screens with openings no larger than 0.5 inches acrosstheir entire length including the downspout opening.

Roof washers Rainwater harvesting systemscollecting water from impervious roofs are required tohave a roof washer for each cistern. Roof washers arenot required for water collected from green roofs orother pervious surfaces. The roof washer is required todivert at least the first 10 gallons of rainfall away fromthe cistern and contain 18 inches of sand, filter fabric,and 6 inches of pea gravel to ensure proper filtration.

Cisterns Material of construction shall be rated forpotable water use. Cisterns shall be able to be filledwith rainwater and the municipal water system. Cross-contamination of the municipal water system shall beprevented by the use of (1) a reduced pressurebackflow assembly or (2) an air gap. Cisterns shall beprotected from direct sunlight.

Piping Piping for rainwater harvesting systems shallbe separate from and shall not include any directconnection to any potable water piping. Rainwater

harvesting pipe shall be purple in color and labeledCAUTION: RECLAIMED WATER, DO NOT DRINKevery four feet in length and not less than once perroom.


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recommendation that special disinfection measures were unnecessary for rainwater dedicated tonon-potable uses.10

The level of treatment required by each municipality can influence the number of harvestingsystems installed. Filtration and disinfection are not expensive treatment requirements but eachtreatment requirement adds a cost to the system. Simplifying the treatment requirements whenthere is not a threat to public health lowers the cost for private entities to install systems andencourages broader adoption of the practice.

Cross-contamination Cross-contamination of the potable water system is a critical concern forany water reuse system. Cross-contamination measures for rainwater reuse systems will besimilar to those for reclaimed and graywater systems. When rainwater is integrated as a

significant supply source for a non-potable indoor use, a potable make-up supply line is neededfor dry periods and when the collected rainwater supply is unable to meet water demands. Themake-up supply to the cistern is the point of greatest risk for cross-contamination of the potablesupply. Codes will require a backflow prevention assembly on the potable water supply line, anair gap, or both. In addition to backflow prevention, the use of a designated, dual piping systemis also necessary. Purple pipes, indicating reused water, are most often used to convey rainwaterand are accompanied by pipe stenciling and point-of-contact signage that indicates the water isnon-potable and not for consumption.

Maintenance and inspection The operation and maintenance of rainwater harvesting systemsis the responsibility of the property owner. Municipal inspections occur during installation andinspections of backflow prevention systems are recommended on an annual basis. For theproperty owner, the operation of a rainwater harvesting system is similar to a private well.Especially for indoor uses annual water testing to verify water quality is recommended as wellas regular interval maintenance to replace treatment system components such as filters or UVlights. The adoption and use of rainwater harvesting systems will add to the inspectionresponsibilities of the municipal public works department, but the type of inspection, level ofeffort, and documentation required will be similar to those of private potable water systems and

should be readily integrated into the routine of the inspection department.

Table 3. Minimum Water Quality Guidelines and Treatment Options for Stormwater Reuse.11


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slightly more than $2 for a thousand gallons. Price, therefore, creates little incentive for conservation orthe use of alternative sources.12

Residential rain barrels are an inexpensive and easy retrofit that reduces stormwaterrunoff and provides irrigation water.Photo at left: District of Columbia Water & SewerAuthority; Photo at right: Ann English.

San Francisco Rainwater Harvesting MOU

In 2008, San Franciscos Public Utilities Commission (SFPUC), Department of Building Inspection (DBI), andDepartment of Public Health (DPH) signed a Memorandum of Understanding for the permitting requirements forrainwater harvesting systems located within the City and County of San Francisco. The MOU encourages rainwater


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To better manage natural resources and water infrastructure, EPA has advocated four pillars ofsustainable infrastructure, one of which is full cost pricing of water. Full cost pricing would result in

water rates that reflect the entire suite of costs associated with water delivery: past, present, and futurecapital costs and operations and maintenance. Full cost pricing would ideally also include the externalcosts associated with the environmental damage and resource depletion created by water use.13, 14

However, user fees and other funding sources are insufficient in 29% of water utilities to cover the cost ofproviding service, let alone including external costs.15 Insufficient pricing is a significant barrier tocollection and reuse.

Water needed for sanitation, cleaning, and cooking is less

responsive to price than discretionary uses such aslandscaping, but overall, water generally displays inelasticdemand. A 10% increase in domestic prices decreases demand2 to 4%; a 10% increase in commercial prices decreasesdemand 5 to 8%.16 While studies show that price has limitedeffect on demand, they also do not consider the option of alow-cost alternative source of water. Increased prices may notsignificantly diminish water use, but may be sufficient toencourage the use of lower cost alternatives. When faced with

sufficiently priced potable water, the investment in a low costalternative that provides continued savings becomesincreasingly favorable.

Regulations and codes also inhibit rainwater collection.Plumbing codes have been identified as a common barrier.Whether they make no provisions for rainwater reuse orrequire downspouts to be connected to the stormwater collection system, thereby eliminating the

possibility of intervening to intercept roof runoff, code changes are often a necessary first step to enablingrainwater harvesting. Other regulations complicate the implementation of rainwater harvesting. Westernwater rights and the doctrine of first in time, first in line access to water can present a barrier to

Albuquerque-Bernalillo County BuildingStandards

In 2008, the Water Utility Authority ofAlbuquerque-Bernalillo County institutednew standards that require rainwaterharvesting systems for new homes.Buildings larger than 2,500 square feet arerequired to have a cistern and pump, whilesmaller buildings can use cisterns, rainbarrels, or catchment basins. All rainwaterharvesting systems need to capture therunoff from at least 85% of the roof area.

The standards also include a requirementfor high efficiency toilets and prohibitionsagainst installing turf on slopes steeperthan 5:1 and sprinkler irrigating areassmaller than 10 feet in any dimension.


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Energy and ClimateIn addition to the natural resources impacts that water use imparts, water collection, treatment, anddistribution has energy and climate consequences. The connection between water and energy is often

overlooked but the process of extracting water from surface or groundwater supplies, bringing it totreatment facilities, treating it to drinking water standards, and delivering it to residential and commercialcustomers expends energy primarily because of pumping and treatment costs. The water sector consumes3% of the electricity generated in the U.S. and electricity accounts for approximately one-third of utilitiesoperating costs.17 Reducing potable water demand by 10% could save approximately 300 billion kilowatt-hours of energy each year.18 Water reuse systems, like rainwater harvesting, supplant potable water andreduce demand. The reduced water demand provided by rainwater harvesting systems translates directlyto energy savings. Table 4 presents estimates of the energy required to deliver potable water toconsumers.

Table 4. Estimated Energy Consumption for

Water Treatment and Distribution.19

Activity

Energy Consumption

kWh/MG

Supply and conveyance 150

Water Treatment 100

Distribution 1,200

Total 1,450

Decreasing potable water demand by 1 million gallons can reduce electricity use by nearly 1,500 kWh.An inch of rainfall produces 600 gallons of runoff per 1,000 square feet of roof. Coordinated residentialapplications and large-scale non-residential rainwater harvesting systems offer an alternative method ofreducing energy use.

Limiting energy demand is significant but the impact that decreased energy demand has on carbon

dioxide emissions is critical. Carbon dioxide emissions associated with electricity generation varyaccording to the fossil fuel source. Rough estimates suggest that reducing potable water demand by 1million gallons can reduce carbon dioxide emissions 1 to 1 tons when fossil fuels are used for power


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Conclusions and RecommendationsEncouraging rainwater harvesting and reuse requires enabling the practice through codes and regulationsand providing incentives. State or municipal codes need to address public health concerns by stipulating

water quality and cross-contamination requirements. Similar to reclaimed and graywater, specificrainwater harvesting codes need to be developed. Codes should establish acceptable uses for rainwaterand corresponding treatment requirements. Disinfection of rainwater for reuse has been the standard, butrecent research and policies should encourage jurisdictions to evaluate lesser requirements for non-potable uses in water closets and urinals. The simplification of the on-site treatment process andassociated cost savings could broaden the use of rainwater harvesting without increasing exposure risks.

In addition to code development, incentives forrainwater harvesting should be instituted. The

incentives should recognize that rainwater is aresource and that the use of potable water carriesand environmental and economic cost. Currentwater policies and rates do not promotesustainability, with a structure that inadequatelyaccounts for the value of water and does notpromote conservation. Municipalities should reviewtheir water rates to see if they appropriately accountfor the full cost of water. Pricing alternatives suchas increasing block rates, which increase the priceof water with increased use, create an incentive toconserve potable water. An increased price ofpotable water would encourage investment inrainwater harvesting systems because they offer along-term inexpensive supply of water after theinitial capital investment. The combined actions ofestablishing certain requirements for rainwater

harvesting systems and increasing the currentlyunderpriced cost of water creates a complementarysystem that can encourage the use of alternative


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Considerations when Establishing a Municipal Rainwater Harvesting Program

1. Establish specific codes or regulations for rainwater harvesting

Building and plumbing codes are largely silent on rainwater harvesting. Consequently, graywaterrequirements are often used to govern rainwater harvesting systems, resulting in requirements that are morestringent than necessary. Codes should define rainwater harvesting and establish its position as anacceptable stormwater management/water conservation practice.

2. Identify acceptable end uses and treatment standards

Each municipality will need to consider and identify acceptable uses for harvested rainwater and the requiredtreatment for specified uses. Rainwater is most commonly used for non-potable applications and segregatedby indoor and outdoor uses.

Typical outdoor uses:

1. Irrigation; and

2. Vehicle washing. Typical indoor uses:

1. Toilet flushing;2. Heating and cooling; and3. Equipment washing.

Non-potable uses typically require minimal treatment. Outdoor uses normally need only prescreening to limitfouling of the collection system. Indoor non-potable uses do not necessarily require treatment beyondscreening, although some municipalities have adopted a conservative approach and require filtration anddisinfection prior to reuse.

Harvested rainwater can be used for potable applications although a special permitting process should be

established to ensure that proper treatment (e.g., filtration and disinfection) is provided and maintained.3. Detail required system components

Jurisdictions often delineate between rain barrels and cisterns because of the size and potential complexity ofthe systems. Rain barrels collect relatively small quantities of water and generally only require mosquitoprevention, proper overflow, and an outlet for outdoor uses. Cisterns can be 100 to several thousand gallonsin size and may be connected to various indoor plumbing and mechanical systems. Needed systemrequirements include:

Pre-filtration Filtration prior to the rain barrel or cistern should be provided to remove solids and debris.

Storage containers Rain barrels and cisterns should be constructed of a National SanitationFoundation approved storage container listed for potable water use.

Back-flow prevention For cisterns that require a potable water make-up for operation, back flowprevention in the form of an air gap or backflow assembly must be provided.

Duel piping system a separate piping system must be provided for harvested rainwater distribution


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Case Studies

King Street Center, Seattle

The King Street Center in Seattle uses rainwater for toilet flushing and irrigation. Rainwater from thebuildings roof is collected in three 5,400 gallon cisterns. Collected rainwater passes through each tankand is filtered prior to being pumped to the buildings toilets or irrigation system through a separatepiping system. When needed, potable makeup water is added to the cisterns. The collection and reusesystem is able to provide 60% of the annual water needed for toilet flushing, conserving approximately1.4 million gallons of potable water each year.21

The Solaire, Battery Park City, New YorkThe 357,000 square foot, 27 floor building was the first high-rise residential structure to receive LEED

Gold certification. The Solaire was designed to comply with Battery Park Citys progressive water andstormwater standards; more than 2 inches of stormwater must be treated on site to meet the standards.Rainwater is collected in a 10,000 gallon cistern located in the buildings basement. Collected water istreated with a sand filter and chlorinated according to New York City Standards prior to being reused forirrigating two green roofs on the building. Treated and recycled blackwater is used for toilet flushing andmake-up water. Water efficient appliances and the rainwater and blackwater reuse system have decreasedpotable water use in the building by 50%.22 Because of its innovative environmental features, the Solaireearned New York States first-ever tax credit for sustainable construction.23, 24

Philip Merrill Building, Annapolis, MDThe Chesapeake Bay Foundationsheadquarters is a LEED Version 1 Platinumcertified building. Rainwater from the roof iscollected in three exposed cisterns locatedabove the entrance.25 Roof runoff passesthrough roof washers before entering thecisterns; following the cisterns the water is

treated with a sand filter, chlorination, staticmixer, and carbon filter prior to reuse. Thebuilding uses composting toilets so the reused


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gallon tank on the buildings roof and a new 50,000 gallon tank installed in the basement. The collectedrainwater is used for toilet flushing, irrigation, and HVAC makeup. A biodegradable blue dye is added tothe water used for toilet flushing to visually identify it as non-potable water. The system reduces potablewater use in the building by several million gallons a year.31, 32

Stephen Epler Hall, Portland State UniversityPSUs 62,500 square foot mixed-use student housing facility (classrooms and academic office space arelocated on the first floor) was completed in 2003 and is LEED Silver Certified. The stormwatermanagement system was designed to be engaging to the public; rain from the roofs of Epler Hall andneighboring King Albert Hall is diverted to several river rock splash boxes in the public plaza.33 Thewater then travels through channels in the plazas brick pavers to planter boxes where it infiltrates and isfiltered before being collected in an underground cistern. UV light is used to treat the water prior to its

reuse for toilet flushing in the first floor restroom and irrigation. Placards located in the water closetsindicate that the non-potable toilet flushing water is not for consumption. The stormwater collection andreuse system conserves approximately 110,000 gallons of potable water annually, providing a savings of$1,000 each year.34, 35

Natural Resources Defense Councils Robert Redford Building, Santa MonicaNRDCs renovation of a 1920s-era structure in downtown Santa Monica achieved LEED NewConstruction, Version 2 Platinum certification. The innovative water systems in the 15,000 square foot

building are a key component of the projectssustainability. The plumbing system deliverspotable water only to locations where drinkingwater is needed, such as faucets and showers.Water from the showers and sinks is collected ingraywater collection tanks and treated on-site. Thetreated graywater is reused for toilet flushing andlandscaping. Rainwater from the building iscollected in outdoor cisterns, which were installed

beneath planters adjacent to the building. Thecollected rainwater is filtered prior to being addedto the graywater collection tank as part of the water


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1 U.S. Government Accountability Office, Freshwater Supply: States View of How Federal Agencies Could Help

Them Meet the Challenges of Expected Shortages, GAO-03-514, July 2003.2 Texas Rainwater Harvesting Evaluation Committee,Rainwater Harvesting Potential and Guidelines for Texas,

Report to the 80th Legislature, Texas Water Development Board, Austin, TX, November 2006.3 American Waterworks Association Research Foundation (AWWARF),Residential End Uses of Water, Denver,

CO, AWWARF, 1999.4 Pacific Institute, Waste Not, Want Not: The Potential for Urban Water Conservation in California , November

2003.5 See note 2.6 Alan Traugott,Reclaimed Water and the Codes, Consulting-Specifying Engineer, April 1, 2007, available at

http://www.csemag.com/article/CA6434236.html (accessed June 2008).7 Susan R. Ecker,Rainwater Harvesting and the Plumbing Codes, Plumbing Engineer, March 2007, available at

http://www.plumbingengineer.com/march_07/rainwater.php(accessed June 2008).8 See note 7.9 City of Portland Office of Planning & Development Review,Rainwater Harvesting ICC RES/34/#1 &

UPC/6/#2: One & Two Family Dwelling Specialty Code: 2000 Edition; Plumbing Specialty Code: 2000 Edition ,March 13, 2001.

10 See note 7.11 See note 2.12 U.S. EPA,Drinking Water Costs & Federal Funding, EPA 816-F-04038, Office of Water (4606), June

2004.13 U.S. EPA, Sustainable Infrastructure for Water & Wastewater, January 25, 2008, available at

http://www.epa.gov/waterinfrastructure/basicinformation.html(accessed June 2008).14 U.S. EPA, Water & Wastewater Pricing, December 18, 2006, available at

http://www.epa.gov/waterinfrastructure/pricing/About.htm(accessed June 2008).15 U.S. Government Accountability Office, Water Infrastructure: Information on Financing, Capital Planning,

and Privatization, GAO-02-764, August 2002.16 U.S. EPA, Water and Wastewater Pricing: An Informational Overview, EPA 832-F-03-027, Office of

Wastewater Management, 2003.17

G. Tracy Mehan,Energy, Climate Change, and Sustainable Water Management, Environment Reporter TheBureau of National Affairs, ISSN 0013-9211, Vol. 38, No. 48, December 7, 2007.18 Michael Nicklas,Rainwater, High Performance Buildings, Summer 2008.19 C lif i E C i i C lif i W E I P bli I E R h P


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28 U.S. Department of Energy, The Philip Merrill Environmental Center, Chesapeake Bay Foundation Annapolis,Maryland, Office of Energy Efficiency and Renewable Energy, DOE/GO-102002-1533, April 2002.

29 Jessica Boehland, Case Study: Alberici Corporate Headquarters, GreenSource.30 Alberici Enterprises,Alberici Corporation Builds Green, 2004, available at

http://www.alberici.com/index.cfm/Press%20Room/Alberici%20Corporation%20Builds%20Green (accessed May2008).

31 National Association of Industrial and Office Properties,Lazarus Building Serves as Example of SustainableDevelopment in Renovation of Community, September 19, 2007, available athttp://www.naiop.org/newsroom.pressreleases/pr07greenaward.cfm(accessed June 2008).

32 Matt Burns, Green Lazarus Building Gets National Accolade, Business First of Columbus, September 25,2007, available at http://columbus.bizjournals.com/columbus/stories/2007/09/24/daily10.html (accessed June 2008).

33 Interface Engineering, Case Study: Stephen E. Epler Hall, Portland State University.34 Portland State Sustainability, Stephen Epler Residence Hall, available at

http://www.pdx.eud/sustainability/cs_co_bg_epler_hall.html(accessed June 2008).35 Cathy Turner,A First Year Evaluation of the Energy and Water Conservation of Epler Hall: Direct and

Societal Savings, Department of Environmental Science and Resources, Portland State University, March 16, 2005.36 Amanda Griscom, Whos the Greenest of Them All NRDCs New Santa Monica Building May be the Most

Eco-Friendly in the U.S., Grist, November 25, 2003, available athttp://grist.org/news/powers/2003/11/25/of/index.html(accessed June 2008).

37 Center for the Built Environment, University of California, Berkeley, The Natural Resources Defense Council Robert Redford Building (NRDC Santa Monica Office), Mixed Mode Case Studies and Project Database, 2005,

available at http://www.cbe.berkeley.edu/mixedmode/nrdc.html (accessed June 2008).38 Natural Resources Defense Council,Building Green CaseStudy, NRDCs Santa Monica Office, February

2006.


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Rainwater Harvesting: Comparing

Storage Solutionsby Doug Pushard

Storage tanks, usually the most expensive component of the rainwater harvesting system,come in a wide variety of sizes and types. When deciding on the type of tank to use, the

main factors to consider include where you live and your budget. When choosing the size of

storage tank or cistern, consider several variables: rainwater supply (local precipitation),

demand, projected length of dry spells without rain, catchment surface area, aesthetics,personal preference, and of course, your budget.

A myriad of variations on storage tanks and cisterns have been used over the centuries and

in different geographical regions: earthenware cisterns in India, large pottery containers inAfrica, above-ground vinyl-lined swimming pools in Hawaii, concrete or brick cisterns in thecentral United States, and, in Texas and Colorado, galvanized steel tanks and site-built

stone-and-mortar cisterns.

Tanks can be above or below ground. Factors such as soil, outside temperature ranges, andcost should be used to determine whether a tank is placed above or below ground. Sometanks are suited for above-ground placement (i.e. vinyl-lined swimming pools), whereothers can be used both above and below ground (i.e. polyethylene). Some types of tanksare built to be buried (i.e. polyethylene tanks designed for burial).

Consequently, understanding all the information about the options available is critical to

making a good decision about the type of tank to purchase, since it should prove to besomething you live with for a long time. Below is a general overview of the various tank

types to choose from and some of their characteristics.

Fib l


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below ground.

Most of the tanks stocked by farm and garden supply

houses are usually for above-ground installations. Forburied installation, specially designed and reinforced

tanks are necessary to withstand soil expansion andcontraction. Polyethylene tanks are comparatively

inexpensive, lightweight, and long-lasting and areavailable in capacities from small 50 gallon barrels to

large 10,000 gallon tanks. They are lighter in weightthan other types of tanks, including fiberglass, andconsequently, are cheaper and easier to transport.

Polyethylene tanks tend not retain paint well, so use pre-painted (i.e. pigmented) tanksmanufactured with opaque plastic. Black and dark colored tanks will absorb heat and thus,

should be shaded or buried. The fittings of these tanks are aftermarket modifications and

are easy to plumb. However, the fittings are not always tight, and should be checked forleakage occasionally.

In-ground polyethyleneIn-ground polyethylene tanks are more costly for

two reasons: the cost of excavation and the cost ofa more heavily reinforced tank.

The latter is required if the tank is to be buriedmore than two feet deep. Burying a tank in soil

with high clay content is not recommended

because of the expansion and contraction cycles ofclay.

For below ground installation, the walls of polytanks must be manufactured thicker, and


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WoodFor personal aesthetic appeal, a wood tank are sometimes a desirable

choice. Wood tanks, similar to water towers at railroad depots, werehistorically made of redwood. However, modern wood tanks are usually

of pine, cedar, or cypress wrapped with steel tension cables. Wood

tanks are lined with plastic to increase longevity. For potable use, afood-grade liner should be used.

Redwood, as a tank material, has a great reputation for being durable and attractive. Itcontains no resins and has high levels of tannin, a natural preservative resistant to insects

and decay. It is also a good insulator, keeping the water cooler in the summer and protects

it from freezing the winter.

These tanks are available in capacities from small 700 gallon tanks to very large 37,000gallon tanks, and are usually site-built by skilled technicians. As with metal tanks, they canbe dismantled and moved to a different location, if required. These tanks are for above-

ground use and not for use in dry, hot climates.

Redwood is very attractive, but it is expensive and not readily available. Pine is commonly

used and although it does not have some of the characteristics of redwood, it is readilyavailable and less expensive.

MetalAs with wood, galvanized sheet metal tanks can also be an attractive option. They areavailable in sizes that range from small tanks of 150 gallons to medium-sized 2,500 gallon

tanks, and are lightweight and easy to relocate if required.

Most tanks are corrugated galvanized steel dipped in hot zincto improve corrosion resistance. These tanks should be lined

with a food-grade liner, usually polyethylene or PVC, orcoated on the inside with epoxy paint. The paint or liner willextend the life of the metal and if being used for potable


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One unique advantage of poured concrete is that the concrete will over time decrease the

corrosiveness of rainwater by leaching into the water. This advantage of concrete tanks

results in a desirable taste imparted to the water by calcium in the concrete being dissolvedin locations where there is slightly acidic rainwater. For potable systems, it is essential thatthe interior of the tank be plastered with a high-quality material approved for potable use.

Underground concrete tanks are prone to cracking and leaking, especially when in clay soil.

Leaks can be easily repaired, although the tank may need to be drained to make the repair.

If building the tank yourself, it is recommended to involve the expertise of a structuralengineer to determine the size and spacing of reinforcing steel to match the structural loadsof a poured-in-place concrete. A product that repairs leaks in concrete tanks, Xypex(TM), is

now available and approved for potable use.

FerrocementFerrocement is the term used to describe a steel and mortar composite material. Thesetanks can be above or below ground and can be done by contractors or homeowners. They

were developed in third-world countries to be relatively low-cost and durable. They are

listed separately from concrete, not just because of the materials used to construct them,but also because they have differing problems and advantages.

These tanks are typically built with concrete, but have multiple layers of wire mesh -typically chicken wire-wrapped around a light framework of rebar, embedded in the

concrete. Walls can be as thin as 1" and still be strong. Consequently, it can cost less to

build than a concrete-only tank. If buying a ferrocement tank, make sure it does not containany toxic compounds in the concrete and that the wires are not visible on the inside of thetank.

Ferrocement, like concrete, will need maintenance and repair as cracks appear. It is

important to ensure that the ferrocement mix does not contain any toxic components. Somesources recommend painting above-ground tanks white to reflect the sun's rays, reduceevaporation, and keep the water cool.


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simply a circle of buried tires with a wire mesh inside covered with plaster. Just like stone or

cement cisterns, they will need periodic maintenance torepair cracks on the inside.

These tanks are meant to be buried and can be very

economical for large tank sizes (i.e., 10,000+gallons/37,900 liters), especially if owner-built. In

earthships, tanks are typically built as an integral part of

the home and can provide cooling in hot climates. Incooler climates, the tops and sides should be insulated toprevent cooling. Care should be taken in building a

plastered tie cistern to ensure the wire mesh and tiresare thoroughly covered with plaster.

As with stone and mason cisterns, these tanks are custom-built, so they can be as large asdesigned. They are typically designed to be circular, but since they are buried, they can be

almost any shape. These tanks, if properly constructed and maintained, will last fordecades.

SummaryA summary of cistern materials is below. Keep in mind that the tank is one of the mostimportant components of the system, typically being the most expensive and the most

permanent. Prices on each type of tank can vary widely depending on your locale, local

labor costs, and the price of raw materials. Check with distributors and other rainwaterharvesters in your area prior to making your final choice.

ExpectedLife

Availability Transportability ExpectedMaint.

BuildYour

OwnFiberglass ++ ++ ++ -- ---polyethylene ++ +++ +++ -- ---


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Tank should be opaque or darker, either upon purchase or painted later, to inhibit

algae growth. For potable systems, storage tanks must never have been used to store toxic

materials. Tanks must be covered and vents screened to discourage mosquito breeding. Tanks used for potable systems must be accessible for cleaning. Install first-flush and screening devices prior to water reaching the tanks to keep it

as fresh and clean as possible. Keep tops of tanks free of debris to make it harder for animals to reach the top of

the tank. Buried tanks should be located in well-drained soil and location.

Water weighs about 8 pounds per gallon so plan your pad, if any, before installingyour tank. Plan where storage tank overflow should be piped or directed to. Keep it away from

underneath your holding tank to prevent pad erosion and to keep animals away.

Pushard, D. Rainwater harvesting: comparing storage solutions. 2007 [downloaded2009 February 19]; Available from:www.harvesth2o.com/rainwaterstorage.shtml .
http://www.harvesth2o.com/rainwaterstorage.shtmlhttp://www.harvesth2o.com/rainwaterstorage.shtmlhttp://www.harvesth2o.com/rainwaterstorage.shtmlhttp://www.harvesth2o.com/rainwaterstorage.shtml


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Tank manufacturers websites

Polyethylene

Norwesco www.norwesco.com

Roth/Fralo www.roth-usa.com

Fiberglass

Containment Solutions www.containmentsolutions.com

Xerxes www.xerxescorp.com

Metal

Corgal www.corgaltanks.com

Modular

ACF Raintank www.acfenvironmental.com


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Fixture Water Requirements

Demand at individual water outlets

Sponsored Links

Each fixture in a water supply system represents a certain demand of water. The table below can be used to

indicate the normal supply requirements of common fixtures.

Fixture

Flow rateMinimum Supply

Pressure

(gpm) (l/min) (psi) (kPa)

Aspirator 2.5 10 8 55

Bathtub faucet 5 19 8 55

Bidet 2 7.5 4 28

Combination fixture 4 15 8 55

Dishwashing machine 4 15 8 55

Drinking fountain jet 0.75 3 8 55

Laundry faucet 1/2" 5 19 8 55

L d hi 4 15 8 55
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Water closet with gravity tank 2.5 10 8 55

Water closet with close coupled

tank, ballcock3 11 8 55

Adding up the numbers to cover all fixtures in a system would give the total demand when all fixtures are used

at the same time. This is almost never a realistic situation for a supply system. A reasonable estimate must be

made based on the simultaneously demand of the fixtures.

Sponsored Links

Related Topics

Water Systems Hot and cold water systems - design properties, capacities, sizing and more

Related Documents

Fixtures and Cold Water Storage Capacities Storage capacities of commonly used fixtures

Hot Water Consumption of Fixtures Design hot water consumption of fixtures - basins, showers, sinks andbaths

Hot Water Content in Fixtures Content of hot water in some common used fixtures - basins, sinks and baths

Converting WSFUto GPMConverting Water Supply Fixture Units - WSFU- to GPM

Sponsored Links

T lB Sh t Li t
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Plastic Pipes - Friction Head Loss

Friction head loss (ft/100 ft) in plastic pipes, PVC, PP, PE, PEH

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The pressure head loss (feet H2O per 100 feet pipe) in straight plastic pipes made of materials as PVC, PP,

PE, PEH or similar, can be estimated from the table below.

The friction head loss are calculated for PVC pipes Schedule 40 with the Hazen-Williams equation and a

Hazen-Williams roughness constant c = 145. Minor loss in fittings must be added.

Pressure Friction Head Loss(ft H2O/100 ft pipe)

Volume FlowNominal Pipe Diameter (inches)

Gallons

PerMinute

(GPM)1)

Gallons

PerHour

(GPH)2)

3/8 1/2 3/4 1 1 1/4 1 1/2 2 2 1/2 3 4 6

Nominal Inside Diameter (inches)

0.493 0.622 0.824 1.049 1.380 1.610 2.067 2.469 3.068 4.026 6.065

1 60 3.3 1.1 0.3

2 120 11.8 3.8 1.0 0.3 0.1

4 240 42.5 13.7 3.5 1.1 0.3 0.1
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70 4200 7.9 3.3 1.2 0.3

80 4800 10.2 4.3 1.5 0.4

90 5400 12.6 5.3 1.9 0.5

100 6000 6.5 2.3 0.6 0.1

125 7500 9.8 3.4 0.9 0.1

150 9000 4.8 1.3 0.2

1)GPM = gallons per minute

2)GPH = gallons per hour

1 gal (US)/min =6.30888x10-5

m3/s = 0.0227 m

3/h = 0.0631 dm

3(liter)/s = 2.228x10

-3ft

3/s = 0.1337 ft

3/min =

0.8327 Imperial gal (UK)/min 1 ft H2O = 0.3048 m H2O = 0.4335 psi = 62.43 lbs/ft

2

Example of Friction Head Loss in Plastic Pipes

A flow of 10 GPMin a 2" pipe gives a head loss of 0.2 feet water column per 100 feetof pipe.

Available :http://www.engineeringtoolbox.com/pressure-loss-plastic-pipes-d_404.html
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Contact name _______________________________

Title (architect, engineer, etc) _____________________

Company __________________________________

Address 1 __________________________

Address 2 __________________________________

Telephone __________________________________

Fax ______________________________

E-mail _____________________________

Job name _______________________________

Address 1 ____________________________

Address 2 __________________________________

Site information

How big is the roof footprint (in sf)? ____________________

What material is used for the roof? ____________________

Does the building use roof drains or gutters and downspouts? _______________

Will all of the piping from the roof come to a central point? _______________

If so, where and with what size pipe? ___________________________________

Is the client interested in an aboveground or belowground system? _______________

What is the site topography and soil type (flat, sloped, rocky, etc)? ___________________________

What is the prefered location for the tank(s) in reference to the building? ________________________

Job information Date ____________________

Site information is collected to determine how the rainwater harvesting system will be configured on the site and

what your total collection potential will be. It is helpful to take photographs of the site or draw a sketch of the

site. You want to be sure that the rainwater harvesting system is feasible and practical before you get to

installation.

If the piping does not come to a central point, how many pipes of what size will need to be connected to the

rainwater system? _________________________________________

How far away from the proposed tank location is the farthest point the harvested water will be used (both


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Demand information

If harvested rainwater will be used indoors:

Is the residence used year-round or seasonally? ________________________________

How many people live in the residence? ___________________

Will the harvested rainwater be used for potable uses (cooking, dish washing, drinking, etc)? (This use will be

dependent on local approval and we can not guarantee potable use.) Y / N

Will the harvested rainwater be used for non-potable indoor uses (toilet flushing, laundry, etc)? (This use will

be dependent on local approval.) toilets (Y / N), laundry (Y/N), other-specify (Y/N)

Are all of the fixtures low-flow or standard? _______________

How many fixtures total will use the rainwater harvesting system? ___sinks___showers___toilets ___other

If harvested rainwater will be used outdoors:

How big is the area to be irrigated (sf)? ___________________

Will the irrigation be sprinklers or drip/high efficiency? ________________

When (day of the year) does irrigation start and end? ______________________________________

If there is an additional outdoor water use (vehicle washing, pool filling, etc), how much harvested rainwater

will be needed per day? ___________

COMMERCIAL

If harvested rainwater will be used indoors:Is the building used year-round or seasonally? ___________________________

H l ill h b ildi ?

The demand information is used to size the tank, size the pump and determine the need for extra purification. We

recommend additional purification with any system that uses harvested rainwater indoors. To size the tank, you

will need to estimate the total daily demand. If the client already has an estimate, record that in addition to these

questions. To size the pump, you will need the peak demand (as well as the distance noted above). Again, if theclient already knows this, record that value. If not, we will use the sum of all the fixture use.

RESIDENTIAL


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GUIDE TO THE RWH SYSTEM

DESIGN WORKSHEETTank selectionStorage volume needed_____________________________(calculated from tank-sizing

spreadsheet)

Aboveground or belowground? _________________

This decision will often be guided by the client's wishes. However, factors that will

affect the decision include space on the site, topography (Will you be able to getappropriate fall in the pipe to an aboveground tank? Will it be possible to bury tanks on

the site (elevation, soil type etc.) and the amount of storage needed.

Tank material: _____________________

For aboveground tanks, tank material is largely based on appearances and cost.

Polyethylene tanks are frequently less expensive, but many clients prefer the look ofmetal tanks. For belowground tanks, a significant consideration is the load that will be

over the tanks. If the tanks are to be used under a road or parking lot that will have heavy

truck traffic, a fiberglass or concrete tank may be most practical. If the tanks are to beused under an area with pedestrian traffic, polyethylene or modular systems may be

appropriate. Polyethylene tanks are often not practical for systems requiring more than

10,000 gallons of storage. Modular systems are beneficial for areas with limited space

because the tank can be configured to fit the available area. Other belowground tankoptions to consider include concrete and sealed HDPE stormwater pipes (such as those

available from ADS). The article by Doug Pushard included in the reference packet

includes more information on the advantages and disadvantages of different tank

materials. The reference material also includes websites for numerous tank retailers andphotographs of tank installations by RMS.


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Will tanks be set sufficiently far away from the footing of the building?

For aboveground tanks, is the ground adequately prepared to set the tanks or will a slabbe needed?

Will all components be sufficiently protected from freezing? Small diameter pipes

aboveground or near the surface should be considered in particular.

Pre-tank filtration selectionRoof footprint to be used (sf) ____________________________

Number of connection points from roof leaders or pipes_____________________

Will filters be aboveground or belowground? ________________________________

In most systems with aboveground tanks, the pre-tank filter is going to be aboveground.

In other situations, the decision is based largely on site topography (to ensure adequate

fall), client preference, and the nature of the drainage system from the roof. The vortexfilters can be used indoors, aboveground in systems with roof drains; the downspout filter

and standpipe filter can only be used outdoors.

Which filter is appropriate? __________________________

Filter selection is

based on total roofarea and whether the

filter will be usedaboveground or

belowground. The

filter options are thedownspout filter, the

standpipe filter, and

the low, medium and high capacity vortex filters. All of these filters can be usedaboveground, but only the vortex filters can be used fully belowground. For roof areasgreater than about 22 000 sf it is usually best to use high capacity vortex filters For


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The number of filters is calculated first by dividing the total roof area by the roof area

appropriate for the filter. Next compare this number to the number of connection pointsto ensure feasibility of the installation.

Check points

Is there appropriate fall from the roof to the filter and the filter to the tank?If you are using downspout filters or standpipe filters, is there enough space for vertical,

round pipe above the filter?

If you are using a vortex filter, is there enough space for 6-8 ft of horizontal pipe before a

high capacity vortex filter and 3-4 ft of horizontal pipe before a low or medium capacityvortex filter?

How will the filter be mounted or buried?Does the pipe size entering and leaving the filter fit with the filter inlets and outlets?

Inlet(s) to the tankHow many outlet pipes from the filters will there be potentially entering the tank and what size

are they? _____________

How many total penetrations to the tank(s) will there be (and what size)? __________________

Much of this decision is going to be based on how many penetrations to the tank are

appropriate, largely based on the type andnumber of tank(s). For example, four 4"

penetrations into a fiberglass tank are likelynot feasible, while four 4" penetrations into a

concrete tank may be simple. You should also

consider the number of pre-tank filters in

determining the number of penetrations intothe tank. Finally, the tank will need to be

vented adequately which may require an

additional penetration.


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Both submersible pumps and jet pumps have advantages. The decision to use a

submersible or jet pump is largely one of preference. Submersible and jet pumps are bothavailable in a variety of sizes to meet most needs. Information on some of the pumps

commonly used by RMS is included in the reference packet.

How many GPM are needed?___________________________

You will want to size the pump to be able to meet the peak demand. This can be

estimated assuming that all fixtures are used at once (based on information gathered

during the site visit). Be sure to only include fixtures plumbed to the rainwater system.

Information on the demand of fixtures can be found in the reference section or athttp://www.engineeringtoolbox.com/fixture-water-capacity-d_755.html

What is the total dynamic head for the system? __________________________ Elements to be considered in determining the total dynamic head for the system include

elevation head, friction loss, pressure loss from filters, pressure head and velocity head.Pressure loss from filters can be found on cut sheets for the filters. Information on

calculating friction loss is in the reference packet or can be found at

http://www.engineeringtoolbox.com/pressure-loss-plastic-pipes-d_404.html.

Which pump is appropriate for the system? ____________________

Use the GPM and total dynamic head calculated above to determine which pump fits

your needs. You may need to use multiple pumps controlled by a multiplex pump controlpanel.

Is a pressure tank needed? If so, what size?________________________________

A pressure tank is needed with all submersible pumps and can be used to reduce pump

start/stops with a jet pump. A guide to sizing pressure tanks can be found in the referencepacket or is available at

http://www.watersystemscouncil.org/VAiWebDocs/WSCDocs/9884303Sizing_a_Pressur

e_Tank_FINAL.pdf . A tank tee package is needed with all pressure tanks.

How many and what type of floating filters are needed? ______________________________ Coarse floating filters should always be used in systems with pre-tank filtration. Because


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contaminants is dependent on the end use of the water. For irrigation systems, there is

often no need for further treatment, though some drip irrigation systems may requirefurther filtration for sediment. For indoor use, an ultraviolet light or ozonator is

recommended to treat the microbiological quality (bacteria, viruses, etc) of the water.

This filtration should be placed after a sediment filter (usually 1, 5, or 10 microns). Acarbon filter can also be used to address issues of odor and taste. The National Standards

Foundation has guidelines for water treatment that may be useful. The EPA also

provides guidelines on water quality and treatment for harvested rainwater. Their

guidance document for rainwater harvesting is included in the reference section and isavailable at http://www.epa.gov/npdes/pubs/gi_munichandbook_harvesting.pdf.

What size and types of filters will be needed? ___________________________________Filters/treatment units should be selected to address the contaminants identified above.

Filters need to be sized to match the GPM output ofthe pump using parallel filters if necessary. Parallel

filters can also make it easier for the client to

change filters without shutting down the system.

Check pointsBe sure that the treatment provided matches any

state or local requirements.

Back-up water supplyWhat is the back-up water supply for this system? _______________________

Most rainwater harvesting systems will need a backup water supply such a municipal or

well-water to meet water demand during periods of low rainfall.

How will the back-up water supply integrate with the rainwater system? __________________ A variety of options are available for integration with the back-up water supply including

an air gap, RPZ, or parallel systems (two outdoor spigots, one from rainwater and one

from the back-up water supply, for a simple irrigation system). The choice of method of


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Will the overflow(s) be pre-made or fabricated for the

job?____________________________________

Pre-made overflow devices are available through Smith/RMS for 4" outlets. Any larger

outlets will require overflow devices fabricated for the job. The overflow should provide

back-flow prevention and skimming of the water surface.

Check points

Ensure that there is no constriction in pipe size from the roof to the end of the overflowsystem

Check that there is sufficient backflow prevention appropriate to the outlet of theoverflow system (i.e., more protection is needed if the system overflows to a combined

sewer than if it daylights over a cliff).


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RWH SYSTEM DESIGN

WORKSHEETThis worksheet was created to guide you through designing a rainwater harvesting

system while generating a component list and estimate. Items identified in blue

match questions explained in theGUIDE TO THE RWH SYSTEM DESIGNWORKSHEET. The information gathered during the site visit or conversation

with the client will help you answer all of the following questions.Tank selectionStorage volume needed_____________________________(calculated from tank-sizing

spreadsheet)

Aboveground or belowground? _________________

Tank material: _____________________

Number and size of tanks: ____________________________Tank (manufacturer and part #) _______________________________

Components needed to connect the tanks______________________________________

Components needed to bed tanks (gravel, etc)_______________________________________

Pre-tank filtration selectionRoof footprint to be used (sf) ____________________________

Number of connection points from roof leaders or pipes_____________________Will filters be aboveground or belowground? ________________________________


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Pump(s) and floating filter(s)Submersible pump or jet pump? ________________________

How many GPM are needed?___________________________What is the total dynamic head for the system? __________________________

Which pump is appropriate for the system? ____________________

Is a pressure tank needed? If so, what size?__________________________________

How many and what type of floating filters are needed? ______________________________

What will be used for pump dry-run protection?______________________________________

Check valve?____________________________________________________________

Additional treatmentWhat is the end use of the water? _____________________________________

What contaminants need to be considered? _________________________________________

What size and types of filters will be needed? ___________________________________

Components for mounting and connecting the filters:________________________________

Back-up water supplyWhat is the back-up water supply for this system? _______________________

How will the back-up water supply integrate with the rainwater system? __________________

Components for the back-up water supply:________________________________________

OverflowWill the system use one or multiple overflows? ___________________________

Will the overflow(s) be pre-made or fabricated for the job?__________________________

Components needed for overflow:_____________________________________________


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45

Storage tank

1Rainwater collection point(roof drains, gutters, etc)

2Rainwater enters the vortexfilter and is processed.

UV

10

4

Smoothing inlet stainless steel flow-calming device to eliminate turbulence ofthe incoming water as it enters the tank

5Floating stainless steel

ti filt

1 2

38

1112

8 Overflow

9 Pressure tank

M

7


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1 1

2

3

4

7

6

58

Storage tank

1 Rainwater collection point (roof drains, gutters, etc)

2 Rainwater enters the vortex filter and is processed.(Possible 90% diverted to storage tank.

5 Floating stainless steel sucti

6 Submersible feed pump

7 Low water cut off float switch


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1 1

2

3

7

6

5

8

Storage tank

4





7 Low water cut off float switch

9


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1 1

2

3

6


2 Rainwater enters the vortex filter and is processed.(Possible 90% diverted to storage tank.)


6 Jet pump

7 Overflow

4

75

Storage tank

M

4

75

Storage tank


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Remaining water from vortex filter tofl


2Rainwater enters the vortex filter and isprocessed. (Possible 90% diverted to

storage tank.)

3

5Floating stainless steelsuction filter


operating at 45 psi7 Low water cut off float

7

6

8

1 1

2

3

Storage tank4

5

109

10

11

Backflow prevention dev

Pressure regulator valve

12 Pressure gauge

1

13

14


62/64

4

7

5

Storage tank

1Rainwater collection point (roofdrains, gutters, etc)

2Rainwater enters the vortex filter andis processed. (Possible 90% diverted

4

Smoothing inlet stainless steelflow-calming device to eliminateturbulence of the incoming water asit enters the tank

910

7 Low water cu

8 Overflow

1 2

3

6

8


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Remaining water from vortex filter tofl


2Rainwater enters the vortex filter and isprocessed. (Possible 90% diverted to

storage tank.)3

5Floating stainless steelsuction filter


7Low water cut off floatswitch (normally open)

7

6

8

1 1

2

3

Storage tank4

5

11

13

1

12

10

11

Backflow prevention dev

Normally closed float swpipe, activates #12 and

water level in the tank

12 Normally closed solenoi

14

9

Belowgrade concrete vault


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1 1

2

3

7

6

5

Balancing line

4

Remaining water from vortex filter to overflow



3

4Smoothing inlet stainless steel flow-calming device toeliminate turbulence of the incoming water as it enters thetank

5 Floating stainless steel suction filter


7 Low water cut off f loat switch

8Overflow goes from the first tank to the second, andfrom the second tank to further stormwatertreatment. Pipes must be the same size as the inlet.

Pressure tank with tank tee pressure switch and

VentUV

10

88

10 Purification kit