WAF Handbook 3 - Fabrication & Installation of Grease Traps and Underground Grease Interceptors

Oct 23, 2026

Uploaded by Kyle

Handbook for the Water Authority of Fiji providing guidance for the fabrication and installation of passive grease traps and underground grease interceptors to improve clean water and sanitation. It explains how grease traps and interceptors separate fats, oil, and grease (FOG) and solids from wastewater before discharge, and why proper sizing, design, and regular maintenance are required to prevent blockages in sewer reticulation and treatment systems. Covers objectives, design principles, installation considerations, and maintenance actions including clean-out responsibilities and disposal of FOG.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages15

Reading Time38 min

AccessFree to download

Acknowledgement

Preface

1. Background

2. Objectives

3. Designs

3.3.1 Under sink grease trap design

3.3.2.1 Under Sink Grease Trap

3.3.3 Underground Grease Interceptor

Table-Dimensions for Underground Grease Interceptors

3.3.4.1 Underground Grease Interceptor

4. Appendices

4.1 FOG Management

4.2 Minimum Pretreatment Requirement for Food Processes

Clean Water and Sanitation for a Better Life WATER AUTHORITY OF FIJI FABRICATION & INSTALLATION OF GREASE TRAPS AND UNDERGROUND GREASE INTERCEPTORS HANDBOOK 2017 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 | | 3.3.3 Underground Grease Interceptor | 14-17 | | Table-Dimensions for Underground Grease Interceptors | 18-19 | | 3.3.4 Guidelines
3.3.4.1 Underground Grease Interceptor | 20-24 | | 4.Appendices
4.1 FOG Management | 25 | | 4.2 Minimum Pretreatment Requirement for Food Proccesses | 26-27 | 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 mandatory 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. Water Authority of Fiji | Fabrication & Installation of Grease Traps and Underground Grease Interceptors 1 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 interceptor 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 acceptable if it is inspected by Water Authority of Fiji technician and is found to be functioning and maintained properly. By: By: & Andrew Kirkwood Hillary Fisher Devi GHD Consultant Graduate Engineer Leader Liquid Trade Waste Authority of Fiji Authority of Fiji By: By: Sharma de Asa Engineer Engineer Authority of Fiji Authority of Fiji Recommended for Approval By By ________________________ _________________________ Soderberg Ravai GM Planning and Design Executive Oﬃcer Authority of Fiji Authority of Fiji 2 Water Authority of Fiji | Fabrication & Installation of Grease Traps and Underground Grease Interceptors 1. BACKGROUND Proper management of Fats, Oils and Grease (FOG) produced by the discharge from kitchens and food preparation a

FAQs

What problem do grease traps and grease interceptors address in Fiji wastewater systems?

They prevent fats, oils, and grease and solids from being discharged into wastewater or sewer lines, which can cause blockages in the sewer reticulation system and the downstream treatment plants.

How do passive grease traps achieve separation of FOG and solids from wastewater?

They rely on the principle that fats, oils, and grease are lighter than water and rise to the surface while heavier debris settles to the bottom during a period of quiet retention.

How often are pump-outs expected to be performed?

Pump-outs must be done several times over a specified period, usually daily for small grease traps and quarterly for larger ones, depending on Trade Waste Policy requirements and local regulations.

Oct 23, 2026

Uploaded by Kyle