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WATER AUTHORITY OF FIJI

FABRICATION & INSTALLATION OF GREASE TRAPS AND UNDERGROUND

GREASE INTERCEPTORS

2017

Clean Water and Sanitation for a Better Life

• A larger sized grease interceptor can be used. For further specifications

• Two or more grease interceptors can be installed in series to cater for the

The first baffle shall extend from the cover above the water level and down to be

The second baffle shall extend from the inside floor of the interceptor and up to

The above mentioned specifications is for the 1000 litre underground grease interceptor. Refer to Table 3.2 for specifications for larger Grease Interceptors.

wishes to use on their property must first be approved by the WAF.

cal to the fixture(s) being served.

• Ensure that it is as close as possible to the building.

• Ensure that it can withstand the external loads being placed on it

• If it is buried and the top of the interceptor is level with the ground

• A protective wall must be erected around it at least 200mm above the

• It must be at least 200mm above the ground level to prevent water run



• If it is partially buried then it must be at least 200mm above the

• If it is placed in an area with limited space then ensure that it has gas

• Two vents, a minimum of 100mm in diameter, open to the atmosphere

• An induct vent, at low or high level directly off the interceptor at the

• An educt vent, at a high level also directly off the interceptor at the

• The educt Vent diverted to at least 2 meters above the highest point of

• Exterior flaps on the openings of the induct and educt vents.

• Inlet compartment• Separation compartment

• Outlet compartment.

e) Certificate of Compliance A certificate of compliance must be provided by the licensed plumbers after

• Remove lid from the top of the interceptor.• Place suction hose into the compartment.• Begin pump out.• Scrape the inside of the compartment to remove FOG that is stuck to

• Continue pump out until all FOG is removed.• DO NOT use degreasers to clean out the grease trap.• DO NOT use hot water to clean out the grease trap as this will only

make the solidified FOG soluble and harder to remove.

HANDBOOK

Water Authority of Fiji | Fabrication & Installation of Grease Traps and Underground Grease Interceptors 1

ACKNOWLEDGEMENT

This handbook is an important tool for people and businesses in the plumbing industry. This serves a great need for the restaurant industry where it is manda-tory to have grease traps or grease interceptors. The success and final outcome of this handbook required guidance and assistance from many people. We acknowledge and express our sincere gratitude towards the following people who have greatly assisted in compiling this handbook.

• Fiji National University, especially Mr Luke Diloi who is also the President for Fiji Institute of Plumbing and Mr Salabogi Mavoa who is the Associate Dean for College of Engineering, Science and Technology

• Town and City Councils • GHD Capacity Building Consultancy.• Sydney Water Corporation, Australia.• Planning and Design Team of Water Authority of Fiji • All the participants who took part in the Fabrication and Installation of

grease trap consultation workshop for contributing bright ideas towards the handbook.

We would like to give our special acknowledgement to the Water Authority of Fiji’s management team for making it possible to publish this handbook.

2

TABLE OF CONTENTS

Pages Acknowledgment 1 Preface 2 1.Background 2.Objectives

3

3.Designs

4

3.3 Designs 3.3.1 Under sink grease trap design

5 - 9

3.3.2 Guidelines 3.3.2.1 Under Sink Grease Trap

10 – 13

Table -Dimensions for Underground Grease Interceptors

18 -19

4.1 FOG Management

20 -24

14 - 17

26-27




























4.2 Minimum Pretreatment Requirement for Food Proccesses

3.3.3 Underground Grease Interceptor

3.3.4 Guidelines3.3.4.1 Underground Grease Interceptor4.Appendices4.1 FOG Management 25


Water Authority of Fiji | Fabrication & Installation of Grease Traps and Underground Grease Interceptors

PREFACE

Grease traps and grease interceptors are devices designed to separate the Fats, Oil and Grease (FOG) and solids prior to discharge into a wastewater disposal system. It protects the wastewater system from blockages due to FOG and solid waste from food preparation areas. Through various inspections, workshops and presentations, it was found by WAF that there was poor or improper grease trap and grease intercep-tor designs and installations. The majority of the small restaurant owners were not aware of grease trap designs, its purpose, the size required or even the maintenance. Many restaurants had grease traps or grease interceptors but were not maintaining them, while others had undersized designs or poor pipework. This handbook details the designs of the passive grease trap and grease interceptors. It informs the user on the fabrication, materials, sizing and manufacturing. It also outlines the installation process that includes; positioning, venting and piping. This handbook also includes; the frequency of clean outs, responsibility for clean outs and disposal, clean out methods and disposal methods of FOG. These designs are a mandatory guideline for new Grease trap designs and are accept-able if it is inspected by Water Authority of Fiji technician and is found to be function-ing and maintained properly.……………………………………………………………………………………………………………………………………….........Prepared By: Assisted By: _______________ & ________________ _______________________Andrew Kirkwood Hillary Fisher Komal DeviGHD Consultant Graduate Engineer Team Leader Liquid Trade Waste Water Authority of Fiji Water Authority of Fiji

Reviewed By: Checked By:

_______________________ ________________________Rahul Sharma Danilo de AsaGraduate Engineer Senior Engineer Water Authority of Fiji Water Authority of Fiji

Recommended for Approval By Approved By

________________________ _________________________Seru Soderberg Opetaia Ravai Acting GM Planning and Design Chief Executive Officer Water Authority of Fiji Water Authority of Fiji

1. BACKGROUND

Proper management of Fats, Oils and Grease (FOG) produced by the discharge from kitchens and food preparation areas is a problem for the Food Industry and for the Water Authority of Fiji's Wastewater Operations. The solids and FOG should not be discharged in waste water or sewer lines as it causes blockages which is an issue for WAF's sewer reticulation system and the treatment plants that eventually receive the discharge.

Grease Traps and Interceptors are designed to separate the FOG and solids from the grey water in discharge from kitchens and food preparation areas. The traps use the physical principal that fats, oils and grease are lighter than water and will rise to the top of a water surface and heavy debris will fall to the bottom of the trap when the mixture is allowed to settle for a period of time in quiet conditions. The longer the wastewater stays in the trap, the better the separation.

However, as the amount of retained grease and solids increases, the working capacity of the trap decreases, retention time decreases and physical separation decreases, resulting in the pass through of solids, fats, oils and grease. To prevent this, grease traps and interceptors have to be regularly maintained by removing both the top grease layer and the settled solids at the base of the trap.

There are two ways to remove the grease layer and settled solids. Either by a. manually removing it or b. through pump outs Option (b) is the approved method especially for the larger grease traps or under-ground grease interceptors. Pump outs must be done several times over a specified period (usually daily for small grease traps and quarterly for the larger ones) depend-ing on the requirements of the Trade Waste Policy and local government regulations.

2. OBJECTIVE Upgrade the current Grease Trap design used by the Restaurant Industry in Fiji and ensure the final designs and guidelines is a standard for installing new units for businesses and residents.

2






























4

3

3. DESIGNS

3.3 DESIGNS

3.3.1 UNDER SINK GREASE TRAP DESIGN

Please refer to the Drawings on the next page

STANDARD DESIGN

WAF has developed standard designs for:1. An Under the sink Grease trap2. An Underground Grease Interceptor

Businesses with seating of between 1 - 69 seats will need to install an underground grease interceptor with a volume of 1000 liters minimum. This interceptor can be fabricated to fit above or below ground.

The under sink grease traps are ONLY for Coffee lounges and Snack Bars. It will have a total volume of 200 liters.

This document includes guidelines on the Fabrication, Installation and Maintenance for each design. It is the minimum requirements and can be used as a guideline for Manufacturers that wish to produce the traps in bulk for distribution.






























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3.3.2 GUIDELINES

3.3.2.1 Under Sink Grease Trap

A. FABRICATION:

a) Total Volume The Under sink Grease Trap shall have a total volume of 200 Litres with

a working capacity of 150 Litres and shall ONLY be used for Snack Bars and Coffee Lounges.

b) SizingThe scaled version of the design will use a ratio of surface area to volume.

E.g. The trap is 0.9m x 0.5m x 0.5m and has a:

Surface Area = 2 x [(L x W) + (L x H) + (W x H)] = 2 x [(0.9 x 0.5) + (0.9 x 0.5) + (0.5 x 0.5)] = 2.3 m2,

Total Volume = L x W x H =0.9 x 0.5x 0.5 = 0.225 m3,

And therefore a surface area to volume ratio of

SA: V = 2.3m2:0.225m3 = 2.3:0.225 = 10.22:1 = 10.22/1 = 10.22 ≈ 10

The ratio must be reduced until the volume (V) is 1.

For situations where the FOG to separated exceeds the working capacity of 150 Litres and is less than 700 Litres, the design for the 1000 litre underground grease interceptor MUST be used.

c) Materials The grease trap must be made from a material that does not corrode and

is suitable for in kitchen use. (i.e. Materials specified for food equipment such as food grade Stainless

Steel Type 316 or HDPE).

If alternative materials wish to be used to fabricate the traps then approval must first be obtained from WAF.

d) Manufacturing• The First baffle shall extend from at least 50mm above the water level to

within 50mm of the inside floor of the trap. • The Second baffle shall extend from the inside floor of the trap to within

100mm of the top of the trap. • The Inlet shall be at least 50mm from the top on the inside of the trap

and the outlet pipe at least 150mm from the inside base of the trap.

e) Alternative Designs Any alternative designs for a under the sink grease trap that a business

may wish to use for their food preparation areas must first be approved by the WAF.

B. INSTALLATION:

a) Positioning the Grease Trap• Grease traps shall be placed as close as practical to the fixture(s) being

served. • It shall be located where it is easily accessible at all times for inspection,

cleaning, and removal of accumulated grease. • It can be placed outdoors if there is a limited amount of space inside the

food preparation area.

b) Piping• All Pipe works must be completed by a licensed plumber.• There shall be no piping inside the Grease trap. • Inlet and outlet piping must be as per the regulations set out by the Fiji National Building Codes and the WAF Grease Trap Design Standards and Guidelines.

c) Venting• No Venting required

d) Access to the Trap• Access to the grease trap shall be through the lid.• Lids can be either left as it is on the trap or clamped down. • For areas in which the trap may be encountered by the public, the trap

lid must be securely fastened to prevent tampering.

e) Certificate of Compliance • A certificate of compliance must be provided by the licensed plumber-

safter the installation of the trap.

• These 200 litre grease traps should be cleaned out on a daily basis. • Traps with a Volume greater than 200 litres and less than 500 litres must

• Businesses must keep a record of the clean outs done. If pump outs are

• First scrape the top layer of FOG off the surface on the inside of the trap

• Using the handles of the perforated tray, gently lift the tray up and hold to allow for the effluent water to drain through it.

• Once drained remove the tray and place contents into a sealed plastic

• Scrape the inside of the trap to remove FOG that is stuck to its inside

• DO NOT use degreasers to clean out the grease trap.• DO NOT use hot water to clean out the grease trap as this will only make

the solidified FOG soluble and harder to remove.

• Remove lid from the top of the trap.• Place suction hose into the trap.• Begin pump out of the trap.

• Scrape the inside of the trap to remove FOG that is stuck to its inside

• Continue pump out until all FOG is removed• DO NOT use degreasers to clean out the grease trap.• DO NOT use hot water to clean out the grease trap as this will only make





























(i.e. Materials specified for food equipment such as food grade Stainless

first be obtained from WAF.

• The First baffle shall extend from at least 50mm above the water level to

• The Second baffle shall extend from the inside floor of the trap to within

• The Inlet shall be at least 50mm from the top on the inside of the trap

may wish to use for their food preparation areas must first be approved

• Grease traps shall be placed as close as practical to the fixture(s) being

• It shall be located where it is easily accessible at all times for inspection,

• It can be placed outdoors if there is a limited amount of space inside the

• All Pipe works must be completed by a licensed plumber.• There shall be no piping inside the Grease trap. • Inlet and outlet piping must be as per the regulations set out by the Fiji

• No Venting required

• Access to the grease trap shall be through the lid.• Lids can be either left as it is on the trap or clamped down. • For areas in which the trap may be encountered by the public, the trap

e) Certificate of Compliance • A certificate of compliance must be provided by the licensed plumber

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3

C. MAINTENANCE:

a) Frequency of Clean Outs• These 200 litre grease traps should be cleaned out on a daily basis. • Traps with a Volume greater than 200 litres and less than 500 litres must

be cleaned every second or third day.• Businesses must keep a record of the clean outs done. If pump outs are

done, then the receipts for the pump out chargers must be kept as this is proof of frequent cleaning.

b) Responsibility for Clean Outs and DisposalIt is the responsibility of the Liquid Trade Waste Permit Holders to ensure that the clean out of the Grease traps are done on a regular basis and disposed of prop-erly.

It is NOT the responsibility of WAF or the relevant authorities to do this. However, it is WAFs and other authorities’ responsibility to monitor the businesses and residents to ensure that this is done regularly and properly.

c) Clean Out Methods

Clean out of the grease traps can be done manually or through pump outs.

For manual removal:• First scrape the top layer of FOG off the surface on the inside of the trap

and place in a sealed plastic bag. Continue this until all the FOG on the surface is removed.

• Using the handles of the perforated tray, gently lift the tray up and hold to allow for the effluent water to drain through it.

• Once drained remove the tray and place contents into a sealed plastic bag.

• Scrape the inside of the trap to remove FOG that is stuck to its inside surface and place into the sealed plastic bag.

• DO NOT use degreasers to clean out the grease trap.• DO NOT use hot water to clean out the grease trap as this will only make


For Pump outs:• Remove lid from the top of the trap.• Place suction hose into the trap.• Begin pump out of the trap.

• Scrape the inside of the trap to remove FOG that is stuck to its inside surface.

• Continue pump out until all FOG is removed• DO NOT use degreasers to clean out the grease trap.• DO NOT use hot water to clean out the grease trap as this will only make


d) Disposal of FOGIf businesses incorporate the under the sink grease trap with an underground grease interceptor, then the removed FOG from the smaller units can be put into the underground interceptor and pumped out when the underground interceptor needs to be cleaned. The removed FOG can then be taken to the Sewerage Treat-ment Plant for disposal.




























3.3.3 UNDERGROUND GREASE INTERCEPTOR

Please refer to the Drawings on the next page

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700 /

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800 -

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- Dim

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(1000 - 5000 Liters)

Typ

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Dim

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800 750

100 100 / 50

100 100

100 665

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5.3 25

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1200 1000

900

2 2000

Inside 1300

1000 900

100 100 / 100

100 100

100 F

81

mesh

8 25

Outside

1500 1200

1100

3 3000

Inside 1700

1000 950

150 150 / 100

100 100

100 F

81

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Outside

2000 1300

1200

4 4000

Inside 1700

1200 1100

150 150 / 100

100 100

100 F

81

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Outside

2000 1500

1350

5 5000

Inside 1700

1400 1250

150 150 / 100

100 100

100 F

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2000 1700

1500

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5

3



20

3

3.3.4 GUIDELINES

3.3.4.1 Underground Grease Interceptor

A. FABRICATION:

a) Total Volume The underground grease interceptor shall have minimum total volume of

1000 litres. Larger interceptors, that have a volume greater than 1000 litres and up

to 5000 litres, can use the dimensions provided in Table 3.2.

b) SizingFor situations where the volume of FOG to be separated exceeds the working capacity of the 1000 litre grease interceptor and is less than that of the 5000 litre grease interceptor:

• A larger sized grease interceptor can be used. For further specifications please refer to the dimensions provided in Table 3.2 to suit the require-ments of the situation

Or• Two or more grease interceptors can be installed in series to cater for the

load.

c) MaterialsThe Interceptor will be made of concrete and be either precast or constructed from the ground up.

Other materials can be used but these must be approved by WAF before it can be manufactured or built.

d) ManufacturingThe first baffle shall extend from the cover above the water level and down to be at least 100mm away from the inside floor of the interceptor and be spaced 250mm away from the inlet.

The second baffle shall extend from the inside floor of the interceptor and up to be at least 200mm away from the cover above and be spaced 300mm away from the outlet.

The vent shall be positioned at opposite sides of the interceptor and be at least 50mm above the water level.(Refer to INSTALLATION part(c) Vents for minimum Vent size)The above mentioned specifications is for the 1000 litre underground grease interceptor. Refer to Table 3.2 for specifications for larger Grease Interceptors.

e) Alternative DesignsAny alternative designs for underground Grease Interceptors that a business wishes to use on their property must first be approved by the WAF.

B. INSTALLATION:a) Positioning of the Underground Grease Interceptor The underground grease interceptor shall be placed as close as practi-


It shall be located where it is easily accessible at all times for inspection, clean-ing, and removal of accumulated grease.

It can be installed indoors or outdoors.

In situations where the interceptor is placed outdoors:• Ensure that it is as close as possible to the building.

• Ensure that it can withstand the external loads being placed on it (vehicles and people).

• If it is buried and the top of the interceptor is level with the ground then all piping for vents and inspection points must not disrupt other utility connections, hinder vehicles or people.

• A protective wall must be erected around it at least 200mm above the ground level to prevent water run offs from seeping into the intercep-tor.

• It must be at least 200mm above the ground level to prevent water run offs from seeping into it (if they grease interceptor will not be.

In situations where the interceptor is placed indoors:• Ensure that it can withstand the external loads being placed on it

(vehicles or people).















5

3



22

3














• A protective wall must be erected around it at least 200mm above the ground level to prevent water runoff from seeping into the interceptor (If the top of the interceptor is level with the ground).

• If it is partially buried then it must be at least 200mm above the ground level to prevent water run offs from seeping into its compart-ments.

• If it is placed in an area with limited space then ensure that it has gas tight lids and proper venting.

b) PipingThere shall be no piping inside the underground grease interceptor. All pipe works must be completed by a licensed plumber.

The inlet pipe will be submerged and therefore the water level inside the trap will be determined by the level of the outlet pipe.

The piping will be completed according to the WAF Fabrication & installation of Grease Traps and Underground Grease interceptors’ guidelines.

Inspection points must be included on the inlet pipe before the interceptor and on the outlet pipe after the interceptor

The inspection points must be a minimum of 100mm in diameter and should be teed off from the inlet and outlet pipes to at least 200mm above the ground level.

c) VentingAll Underground Grease Interceptors must have:• Two vents, a minimum of 100mm in diameter, open to the atmosphere

to allow for cross ventilation.• An induct vent, at low or high level directly off the interceptor at the

inlet compartment. • An educt vent, at a high level also directly off the interceptor at the

outlet compartment.• The educt Vent diverted to at least 2 meters above the highest point of

the building (where necessary).• Exterior flaps on the openings of the induct and educt vents.

Plumbers must ensure that the vents are installed properly so that siphoning does not occur within the chambers of the interceptor.

d) Access to the InterceptorAccess to the Grease interceptor shall be though one of three lids above the:• Inlet compartment• Separation compartment and • Outlet compartment.

e) Certificate of Compliance A certificate of compliance must be provided by the licensed plumbers after the installation of the trap.

C. MAINTENANCE:a) Frequency of Clean OutsThe interceptor should be cleaned on a fortnightly basis through pump outs.

Grease interceptors with a volume greater than 1000 litres and less than 3000 litres must be cleaned out at least every month.

If business owner(s) wish to pump out their underground grease interceptors more frequently (such as weekly) they are allowed to do so.

b) Responsibility for Clean outs and DisposalsIt is the responsibility of the Trade Waste Permit Holders to ensure that the clean outs of the Grease traps/interceptors are done on a regular basis and disposed of properly.

It is NOT the responsibility of WAF or the relevant authorities to clean out the traps/interceptors. However, it is WAFs and other authorities’ responsibility to monitor the businesses or residents to ensure that this is done regularly and properly.

c) Clean out Methodsa) Clean out of Underground grease interceptors can be done through pump outs.






24

























For Pump outs:• Remove lid from the top of the interceptor.• Place suction hose into the compartment.• Begin pump out.• Scrape the inside of the compartment to remove FOG that is stuck to

its inside surface.• Continue pump out until all FOG is removed.• DO NOT use degreasers to clean out the grease trap.• DO NOT use hot water to clean out the grease trap as this will only


d) Disposal of FOGFOG that is removed through pump outs can be disposed by the bailing trucks.

4. APPENDICES

4.1 FOG MANAGEMENT

CHECKLIST FOR MANAGING FAT, OILS AND GREASE IN THE KITCHEN

DO's DON'Ts

Wipe and scrape plates, pots, pans and utensils before washing it in the sink (place all these food scrapings into the rubbish bin) × Do not pour Cooking Oil, Fat or

Grease down the sinks

Collect Waste Oil in a suitable secure container. ×

Do not pour Waste Oil, Fat or Grease down the drains

Use sink strainers in sink holes and empty solid contents from the strainer into the rubbish bin. ×

Do not put food scrapings into the sink. Put it into the rubbish bin.

Regularly clean out and maintain grease traps. ×

Do not sweep waste into floor drains. Collect and place it in the rubbish bin.

Get a licensed waste management company to collect and dispose of FOG from grease traps ×

Do not pour boiling hot water down the sink to dissolve fat and grease.






























26

4.2 MINIMUM PRETREATMENT REQUIREMENTS FOR FOOD PROCESSES

Commercial process

Seats/bed

s

Minimum pretreatment

in floor and in sink bucket traps

Supermarket with chicken cooker

1500 L yes

BBQ wholesale (chicken) 1500 L yes

BBQ wholesale (pork, duck)

2000 L yes

BBQ restaurant 2000 L yes

Hotel/motel kitchen 1-69 1000 L yes






Butchers – retail (no cooking)

1000 L yes

Fish (fresh outlet) no cooking

Large basket trap with fixed screen and removable basket

yes

Chicken (fresh retail) no cooking

1000 L yes

Bakery retail –hot bread - cakes

No grease trap yes

Bakery retail – pies – sausage rolls

1000 L

Commercial process Seats/beds

Minimum pre-treatment

in floor and in sink bucket traps

Cafeteria, canteen (and school hot meals)

1000 L yes

Take-away, including food court shops

1000 L yes

Snack bar – coffee lounge Under sink yes

Restaurant

1-69

1000 L

yes

Restaurant

70-199

1500 L

yes

Restaurant

200-399

2000 L

yes

Restaurant

400-599

3000 L

yes

Restaurant

600-799

4000 L

yes

Restaurant 800-1000 5000 L yes

Kitchen – hospital, nursing home

1-69

1000 L

yes


70-199

1500 L

yes


200-399

2000 L

yes


400-599

3000 L

yes


600-799

4000 L

yes


800-1000

5000 L

yes

McDonalds

1500 L – 3000 L

yes

Pizza Hut Restaurant 1000 L yes

Function centre

1-69

1000 L

yes

Function centre

70-199

1500 L

yes

Function centre

200-399

2000 L

yes

Function centre

400-599

3000 L

yes

Function centre

600-799

4000 L

yes

Function centre

800-1000

5000 L

yes

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