rainwater harvesting 101 - portland or usa

8/9/2019 Rainwater Harvesting 101 - Portland OR USA

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WELCOME THE RAINWELCOME THE RAIN

RAINWATER HARVESTING

101


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What is rainwater harvesting?What is rainwater harvesting?

Rainwater harvesting is theprocess of collecting rainwaterfrom a designated impervious

surface for use some other way. Harvested rainwater is often

used:

for irrigation for non-potable purposes

sometimes for potable purposesCompliments of OASIS DESIGNS


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Parts of a SystemParts of a System

Collection Surface Initial conveyance

Gutters and Downspouts

Roof washer

Holding tanks - Cisterns

Distribution and Fixtures


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Collection SurfaceCollection Surface

Non-pedestrian non-vehicularsurfaces

Roof surfaces

Any allowable roofing material

Metal surfaces work best

Why? Limiting the surface to non-pedestrian

surfaces assists in the prevention ofintroduction of foreign matter into the system


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Collection surfaceCollection surface (continued)(continued)

Roof Area Calculations In an average rain event, for each inch

of rainfall each square foot of roof

typically collects .6233 gallons of rain.Of that 25 to 30 percent is typically lost

before entering the holding tank/cistern.

SUPPLY ( Gallons ) = (CATCHMENT AREA ( FT2 ) xRAINFALL ( inches )) x( .75 x .6233 GAL/CF)


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Collection surfaceCollection surface (continued)(continued)

Calculations continuedCatchment area = 2,000 sq ft

Average annual rainfall = 25 inches

Average collection/sq ft area/inch ofrainfall = .6233 gal/inch

Average collectable amount = 75%

Supply = (2,000 x 25) x (.75 x .6233)orSupply = 23,374 gal annually


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Initial ConveyanceInitial Conveyance

Gets the water from the roof to thecistern.

Gutters

Any gutter material will work in a storm. wider gutters will allow for more water to be

conveyed during a heavier storm.

Gutter Screens Downspouts

Big wide downspouts


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Roof WasherRoof Washer

The roof washer is the fist level offiltration in a full system and theprimary level of filtration in a partial

system. Roof washers serve two purposes:

Divert the first 10 gallons of water from

entering the cisterns

Filter the water before it enters thecistern


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Roof WasherRoof Washer (continued)(continued)

Construction Inlet pipe/ opening

Holding Chamber

Filter medium Filter fabric

Fine sand or

gravel

Outlet pipes First Flush

Cistern

Overflow


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Roof WasherRoof Washer (continued)(continued)

Ready for installation Water Filtration Company

Bushman Corporation

Construct your own


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Roof Washer Detail Number 1Roof Washer Detail Number 1


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CisternsCisterns

Cisterns are the storage facilities forrainwater systems.

Can be located above or below

ground

Made of a variety of materials

recommended that they are created ofmaterials that can be used for potablewater.


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CisternsCisterns (continued)(continued)

SizeUse estimations

Family of 4 average use between 40 and 60

gallons per day, or between 10 and 15 gallons per individual

Minimum Size Requirements

State of Ohio - 2,500 gal. City of Portland- 1,500 gal.

Texas provides no minimum


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Location ConsiderationsGeneral

Always in conformance with MFGs

instructions Accessible


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Location considerationsAbove ground

Flat land

Year round protection from sunlight Structurally sound

Height to width ratios

Not aesthetically displeasing


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Location considerationsBelow Grade

Not a tripping hazard

Listed for burial


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OpeningsScreen protection recommended

Locks where necessary

Inlets

Above cistern floor

Situated to create as little disturbanceas possible.

Potable water backup


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OutletsOutflow pipe above floor

6 - 18 inches

Avoids muckAway from inlet

Hooks to distribution piping

OverflowsLocated toward top of cistern

Discharge location approved


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Cistern Detail Number 1Cistern Detail Number 1


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Cisterns - Above GradeCisterns - Above Grade

Complements of Norwesco

Compliments of Inside Out


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Cisterns - Below GradeCisterns - Below Grade

Compliments of Sir-Tanks A lot

Compliments of Norwesco


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CisternsCisterns--EngineeredEngineeredandand ConstructedConstructed

Compliments of Peter L. Pfeiffer


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Collection Initial Conveyance DetailCollection Initial Conveyance Detail


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Collection Initial Conveyance DetailCollection Initial Conveyance Detail

Compliments of Bushman Corporation


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Distribution and FixturesDistribution and Fixtures

Pumps, Filters and PipesPumps

Properly sized for system

Consider potability factor Pressure tank?

Filters and Treatment

At this stage, only necessary for potablesystems.

Sediment filter

UV Filter


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Distribution and FixturesDistribution and Fixtures (Continued)(Continued)

PipesPotable Systems

Traditional plumbing

Combination Systems Separate and separated from piping for

potable system

Separation in trenches and wall cavities Cross connection protection


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FixturesUtilize standard plumbing fixtures


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MaterialsAny allowed under code

Clearly identified as non-potable water

Purple pipe Continual Mylar marking

Other clear-continual marking

Fittings and other components appropriateto system.


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Clear identification in obvious locationsPipes

Fixtures

All installations per coderequirements


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Distribution to Fixtures DetailDistribution to Fixtures Detail


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Other ConsiderationsOther Considerations

System maintenance System abandonment

Recording

Jurisdiction considerations

Liability Permits

Inspections Planning and zoningFees


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Additional ResourcesAdditional Resources

Oasisdesign.net

General information including design considerationsand resource guide

Ohio Department of Health

Plans for developing a cistern water supply (revised

6/82) www.odh.state.oh.us

Texas Guide to Rainwater Harvestingwww.twdb.state.tx.us/assistance/conservation/Rain.htm

NW Green Directory www.nwgreendirectory.com

Sustainable Building Sourcebook

www.greenbuilder.com/sourcebook/Rainwater.html

rainwater harvesting 101 - portland or usa

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