Guidance Document for Sizing and Installation of Grease Traps, Interceptors and Separators - Part I - Guidance for Grease Trap/Grease Interceptor Sizing and Design Criteria

Oct 23, 2026

Uploaded by Callum

Guidance for San Jacinto River Authority (SJRA) sizing and installation of grease traps, grease interceptors, and separators for commercial food service facilities. The document states applicability for new construction, remodels, ownership/occupancy changes, and sites struggling to meet maintenance or wastewater discharge limits. It provides design and sizing criteria based on UPC and local code expectations, including hydro-mechanical and gravity types, and includes formula methods, flow-rate tables, and stepwise calculations to determine minimum grease trap/ interceptor capacity for compliance with discharge requirements.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages17

Reading Time43 min

AccessFree to download

Part I: Guidance for Grease Trap/Grease Interceptor Sizing and Design Criteria

Introduction

Applicability

Sizing Requirements

Grease Trap/Grease Interceptor Sizing Formulas

Hydro-mechanical Grease Trap Sizing (Pipe Size and Flow Rate)

Gravity Grease Trap/Grease Interceptor

SAN JACINTO RIVER AUTHORITY GUIDANCE DOCUMENT FOR SIZING AND INSTALLATION OF GREASE TRAPS, INTERCEPTORS AND SEPERATORS Part I: Guidance for Grease Trap/Grease Interceptor Sizing and Design Criteria A. Introduction: Information contained within this document is based on standard industry practices and guidance found in the Uniform Plumbing Code (UPC) and the City of Houston Plumbing Code. Size, type, and location of grease traps/grease interceptors shall be in accordance with the manufacturer’s instructions, the requirements of San Jacinto River Authority (SJRA) and the City of Houston Plumbing Code. B. Applicability: These requirements are applicable to all commercial food service establishments, including those that are undergoing: 1. New Construction 2. Interior remodeling to accommodate expansion or operational modifications 3. Changes of ownership/occupancy 4. Facilities which may be experiencing difficulty in achieving compliance with maintenance and/or wastewater discharge limitations. Waste discharge in establishments from fixtures and equipment which contain grease, including but not limited to, scullery sinks, pot and pan sinks, dishwashers, soup kettles, and floor drains located in areas where grease-containing materials exist, shall be permitted to be drained into the sanitary waste through the grease trap/grease interceptor when approved by SJRA. C. Sizing Requirements: Sizing methods described herein are intended as guidance in determining grease trap/grease interceptor sizes that will afford the POTW’s sanitary sewer system a minimum degree of protection against grease and other obstructing materials. Sizing determinations are based on operational data provided by business owners or their contractors. In approving a customer’s plumbing or grease trap design, the SJRA does not accept liability for the failure of a system to adequately treat wastewater to achieve effluent quality requirements specified under SJRA Grease Order. It is the responsibility of the generator and/or contractors to ensure the appropriate level of treatment necessary for compliance with federal, state and local regulations. D. Grease Trap/Grease Interceptor Sizing Formulas: It is the responsibility of the generator and his/her contractors to ensure that the wastewater discharged from the facility is in compliance with the SJRA’s discharge limitations. For the purpose of plans review, a general assessment of grease trap/grease interceptor design and size will be performed using the following formulas. (These formulas have been demonstrated as industry standards capable of achieving the SJRA’s discharge criteria when systems are maintained in proper condition.) Hydro-mechanical Grease Trap: The Hydro-mechanical Grease trap design type incorporates air entrapment, the buoyancy of grease in water and hydro mechanical separation with interior baffling for grease, FOG (fats, oils and grease) separation. Hydro-mechanical Grease traps continuously separate the FOG atthe velocity it enters the interceptor. The size of Hydro-mechanical Grease traps is expressed in the gallons per minute flow (GPM) that the grease trap can accept and still remove the grease and FOG from the influent. On the other hand, the size of a Gravity Grease Interceptor is based on the actual volume of water the interceptor will hold expressed in gallons. Hydro-mechanical Grease Trap Sizing By Pipe Size, Using Gravity Flow Rate (Using Uniform Plumbing Code) Where fixture dimensions and flow rates are unknown, sizing may be achieved by calculating flow through primary drainage line using following Table (Table 10-2 of Uniform Plumbing Code): | Uniform Plumbing Code Table 10-2 | | | | | --- | --- | --- | --- | | Diameter of Grease Waste Pipe | Maximum Full Pipe Flow (gpm) 1 | Size of Grease Trap | | | | | 1-Minute Drainage Period (gpm) | 2-Minute Drainage Period (gpm) | | 2” | 20 | 20 | 10 | | 3” | 60 | 75 | 35 | | 4” | 125 | 150 |

FAQs

What facilities are covered by the grease trap/grease interceptor guidance?

The requirements apply to all commercial food service establishments, including new construction, interior remodeling, changes of ownership/occupancy, and facilities having difficulty meeting maintenance or wastewater discharge limitations.

How are hydro-mechanical and gravity grease units sized differently?

Hydro-mechanical grease trap size is expressed as gallons per minute (GPM) flow that the unit can accept while removing FOG. Gravity grease interceptor size is based on the volume of water the interceptor will hold, expressed in gallons.

What inputs are used to determine grease trap sizing when fixture dimensions or capacities are known?

The guidance provides methods using fixture dimensions (length, width, depth) and drainage period, or using fixture load/hydrant capacity for rated appliances. It instructs calculating drainage volume, applying a fill factor, adding known appliance capacities, then dividing by a one- or two-minute drainage period to obtain the minimum size.

Oct 23, 2026

Uploaded by Callum