Commercial Plumbing Service: Grease Trap Installation and Repair


Part I: Guidance for Grease Trap Sizing and Design Criteria

A. Introduction:

Information contained within this document is based on standard industry practices and guidance found in both the 2009 International Plumbing Code (IPC) Commentary and the Uniform Plumbing Code (UPC), Appendix H. Size, type, and location of grease traps shall be in accordance with the manufacturers’ instructions, the requirements of City of Fort Worth Environmental Ordinance #12274 and Plumbing Ordinance #15951.

B. Applicability:

These requirements are applicable to all commercial food service establishments, including those that are undergoing:
• New construction
• Interior remodeling to accommodate expansion or operational modifications
• Changes of ownership/occupancy
• Facilities which may be experiencing difficulty in achieving compliance with maintenance and/or wastewater discharge limitations

C. Sizing Requirements:

Sizing methods described herein are intended as guidance in determining grease trap/interceptor sizes that will afford the City’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 interceptor design, the City does not accept liability for the failure of a system to adequately treat wastewater to achieve effluent quality requirements specified under Ordinance 12274. It is the responsibility of the generator and/or contractors to insure the appropriate level of treatment necessary for compliance with environmental and wastewater regulations.

Minimum acceptable grease trap/interceptor sizing shall be accomplished as follows:
• Sizing according to formulas found in Section D below.
• Where sizing formulas result in determination of a grease trap less than 750 gallons in capacity, this minimum size is recommended for all restaurant applications. However, under no circumstances should exterior grease traps less than 500 gallons be utilized.

D. Grease Trap Sizing Formulas:

It is the responsibility of the generator and his/her contractors to ensure that the wastewater discharged from their facility is in compliance with the City’s discharge limitations. For the purpose of plans review, a general assessment of grease trap/interceptor design and size will be performed using the following formulas. (These formulas have been demonstrated as industry standards capable of achieving the City’s discharge criteria when systems are maintained in proper condition.)

Method 1: Uniform Plumbing Code, Appendix H

Number of meals x waste flow x retention x storage = size requirement
Per peak hour (1) rate (2) time (3) factor (4) (liquid capacity)

1) Number of meals served at peak operating hour (Seating Capacity) x Peak Factor
a. Where Peak Factor for Fast Food Restaurant is………1.33
b. And, Peak Factor for all other food service types is….1.00
2) Waste Flow Rate:
a. With Dishwasher…………………………………6 gallon flow
b. Without Dishwasher………………………………5 gallon flow
c. Single Service kitchen…………………………… 2 gallon flow
d. Food waste disposer…………………………….. 1 gallon flow
3) Retention Times
a. Commercial kitchen waste/dishwasher…………….2.5 hours
b. Single service kitchen/single serving………………1.5 hours

e.g. (Kitchens that have a three compartment sink, hand sink and mop sink and use disposable cups, plates, forks, knives and spoons.)
4) Storage Factors
a. Fully equipped commercial kitchen …..8 hr operation…1
b. ………………………………………….16 hr operation…2
c. ………………………………………….24 hr operation…3
d. Single Service Kitchen………………………………….1.5

The Uniform Plumbing code includes a built-in safety factor that can yield very large grease trap size specifications. At this time, the City is not requiring traps larger than 4,000 gallons. However, the decision to use a trap smaller than that specified by the formula and calculations above is to be addressed in the plan submission.

Method 2: Alternative Method Supplied by Professional Engineer or Master Plumber
• Must include all calculations with specific site on submitted plans.
• Sealed plans must be submitted to the Water Department by a Texas Licensed Professional Engineer.
• Must show all calculations with recommended size.
• Plans must submit to the Water Department for review and approval.
• Failure to include all of the above will result in the use of the UPC size criteria.

E. Alternate Sizing Formulas / Proposals

Food service establishments that propose the use of alternate sizing techniques and/or procedures that result in specifications that differ from calculated requirements (or are less than the MINIMUM 750 gallon recommendation), must submit formulas and other bases to support proposed grease trap size/ installation. Submission should also provide documentation of ability to meet effluent quality requirements. This proposal must be signed by a licensed plumbing contractor or professional engineer. Under no circumstance will a grease trap smaller than 500 gallons be accepted.

Alternate procedures for grease removal (i.e. Big Dipper, Zurn, Schier, etc.) must be approved on a case by case basis.

F. Construction/Installation:

All permitting, construction, and inspection activities must be completed in accordance with the Fort Worth Plumbing Code #15951. Additionally, the following specifications must be incorporated into grease trap design.
• The grease interceptor shall be constructed with a minimum of two baffles. Each manhole access shall be minimum 20” diameter clear opening. Manhole covers shall be placed at grade elevation by using concrete extension rings or 24” RCP. Side connections are prohibited for inlet or outlet. Inlet and outlet risers are required and shall be factory installed or installed by contractor.
• Grease traps are to be installed at a minimum distance of 10 ft. from sinks and dishwashers to allow for adequate cooling of the wastewater. Water temperatures must be less than 120 degrees prior to entering grease trap.
• All grease bearing waste streams should be routed through an appropriate grease trap/interceptor, including: three-compartment sinks, pot/pan sinks, soup kettles, hand-washing sinks, automatic dishwashers, mop sinks and floor drains. All drains that receive “clear waste” only, such as from ice machines, condensate from coils and drink stations, located in food preparation areas must be plumbed to the oil & grease interceptor. Any exceptions for by-pass must have written authorization from the Chief Plumbing Inspector or the Fort Worth Water Department Director.
• Kitchens that utilize Garbage Disposals shall be required to use an interceptor twice the size calculated in Part I, Section D, above.
• All exterior or recessed Grease Traps and Interceptors are to be installed with an Effluent Sampling Well, equivalent to: a. Parks Equipment Services Sample Well SWB-1; or b. PW Eagle Sample Well. Sample wells will have a minimum 12” diameter access cover. Mechanical Traps and Interceptors that are installed above ground must be equipped with an influent flow regulator and an effluent valve assembly that allows for sample collection.

G. Customer (Generator) Responsibilities:

It is the responsibility of the customer (waste generator) to insure compliance with the City of Fort Worth’s discharge limitations specified in Environmental Ordinance #12274. Hazardous wastes, such as acids, strong cleaners, pesticides, herbicides, paint, solvents, or gasoline should not be disposed of where they would go through grease or grit traps. If commercial dishwashers are discharged through a grease interceptor, care must be taken in system design. Dishwashers use detergents and elevated water temperatures that will melt grease. If the interceptor is either too small or too close to the commercial dishwasher, grease may pass through the interceptor and into the collection system.

Generators are responsible for maintaining grease traps in continuous proper working condition. Further, generators are responsible for inspecting, repairing, replacing, or installing apparatus and equipment as necessary to ensure proper operation and function of grease traps and compliance with discharge limitations at all times.

The generator must have grease traps serviced (pumped, cleaned, and inspected) by a City of Fort Worth permitted waste hauler, at a minimum frequency of every 90 days or more often as necessary, to ensure proper function. Records of maintenance are required to be maintained on site for five (5) years. (90 day maintenance frequency assumes proper sizing and installation consistent with this guidance).

Enzymes, solvents, and emulsifiers are not permitted as they will only change the form of grease, allowing it to be carried out of the trap with the wastewater and deposited in the collection system. Biological treatment systems must be pre-approved by the Pretreatment Services Division. These systems will not alleviate the necessity for inspection and proper maintenance.

Part II: Other types of Interceptors and sizing requirements

Interceptors are required for oil, grease, sand and other substances harmful or hazardous to the building drainage system, the public sewer or sewage treatment plant. Design, size, and location of pretreatment devices must be submitted by a licensed plumbing contractor or professional engineer for review and approval.

A. Laundries

Commercial Laundries, Laundromats, and dry-cleaners shall be equipped with an interceptor in order to reduce the quantity of lint and silt that enter the collection system. The system must be of adequate size and design to allow for cool-down of wastewater so that separation can be more readily achieved. The interceptor must be installed with a wire basket or similar device, removable for cleaning, that prevents passage into the drainage system of solids 1⁄2 inch (12.7 mm) or larger in size, string, rags, buttons or other materials detrimental to the public sewerage system.

Sizing must be in accordance with guidance found in the Uniform Plumbing Code (UPC), Appendix H which uses the following formula:

(TGC) x (CPH) x (RT) x (ST) = Size of Lint Interceptor (gallons)

TGC = Total Gallons per Cycle
CPH = Cycles per hour
RT = Retention time
• 2.5 for Institutional Laundry
• 2.0 for Standard Commercial Laundry
• 1.5 Light Commercial Laundry
ST = Storage Factor, based on hours of operation
• 1.0 for 8 hours of operation
• 1.5 for 12 or more hours

Currently, an effluent sample well is required for all small commercial laundries. However, large and/or industrial laundries may be subject to Federal Pretreatment regulations. For more information please contact the Fort Worth Water Department, Pretreatment Services Division, at (817) 392-8305.

B. Car Washes

Where automobiles are washed (including detail shops utilizing hand-wash practices), separators shall have a minimum capacity of 1000 gallons for the first bay, with an additional 500 gallons of capacity for every other bay.

Additionally, wash racks must be constructed to eliminate or minimize the impact of run- off from rain/storm events. Minimum requirements are roofed structures with at least two walls and appropriate grading to prevent storm water infiltration into the sanitary sewer.

An effluent sampling well is required, per specifications listed in Part I, Section F, Sub- section e.

C. Automotive Repair Facilities (Garages and Service Stations)

Where automobiles are serviced, greased, or repaired or where gasoline is dispensed, oil/water separators shall have a minimum capacity of 500 gallons for the first 1000 square feet of area to be drained, plus 250 gallons for each additional 1000 square feet of area to be drained into the separator. An effluent sampling well is required, per specifications listed in Part 1, Section F, Sub-section e.

Note: Parking garages in which servicing, repairing, or washing is not conducted, and in which gasoline is not dispensed, shall not require a separator. Areas of commercial garages utilized only for storage of automobiles are not required to be drained through a separator, provided there are not connections to the sanitary sewer.

D. Elevators

City of Fort Worth Ordinance requires an oil & grease interceptor for elevators that utilizes hydraulic fluid and must have the capacity to contain all of the hydraulic fluid for the sum of all elevators. The elevator company must provide for each elevator the dimensions for the elevator reservoir [length x width x depth], piping [length x diameter] and plunger [length x diameter] units must be in feet and inches. Data will be used to calculate maximum oil capacity – See. Section 12.5-713(f).

Grease Traps –It is recommended that grease traps be located outside the building, if possible, and
serving all sinks, dishwashers and floor drains in the food preparation areas; otherwise, the grease
trap must be flush-floor mounted with a sealedlid, preferably outside the food preparation area and
must comply with the plumbing/mechanical code.

What is a grease trap/grease interceptor?

A grease trap (or interceptor) is a plumbing device designed to physically separate grease and solids from kitchen wastewater.

What is the difference between a grease trap and a grease interceptor?

Grease traps and grease interceptors are both plumbing devices for grease removal from industrial wastewater discharge streams. The grease trap is generally thought of as the smaller indoor device, usually less than 100 gallons of liquid holding capacity, and, until recently, typically installed below a sink. Grease traps are usually made of steel and often designed with just a single compartment. The grease interceptor is generally considered the large pre-cast concrete tank, typically with a liquid holding capacity anywhere from 250 to 5,000 gallons and designed with two separate compartments. For the purposes of this website, the term “grease trap” is used to describe both devices.

In Dallas, a grease trap is required for any commercial or institutional food service operation.

How often must my grease trap be cleaned?

The Dallas City Code, Chapter 19, Sec 19-126.2 (c) specifies all grease traps must be completely emptied and cleaned by a licensed hauler. The interceptors must be cleaned as often as necessary but not less than every 90 days, or whenever 25% or more of the interceptor contains floating materials, sediment, oils, or grease.

How do I dispose of grease trap waste?

Grease trap waste must be transported by a liquid waste hauler licensed by the Texas Commission on Environmental Quality and Dallas Water Utilities to a properly permitted disposal site

38. Paragraph 1003.3.1, “Grease Interceptors and Automatic Grease Removal Devices Required,”
of Subsection 1003.3, “GreaseInterceptors,” of Section 1003, “Interceptors and Separators,” of Chapter 10, “Traps, Interceptors and Separators,”

1003.3.1 Grease interceptors andautomatic grease removal devices required.
A grease interceptor or automatic grease removal device shall be required to receive the drainage from
fixtures and equipment with grease-laden waste located in food preparation areas,
suchasin restaurants, hotelkitchens,hospitals,school kitchens,bars,factorycafeteriasand
clubs. Fixtures and equipment capable of generating or receiving grease-laden waste shall
include, but not be limited to,pot sinks, pre-rinse sinks; hand sinks; 3-compartment sinks;
rnp sinks ;soup kettles or similar devices; wokstations; floor drains[or] floors inks[into
automatic hood wash units and dishwashers without pre-rise sinks.
Grease interceptors and automatic grease removal devices shall receive

What is a grease interceptor?  

 A grease interceptor is a wastewater pretreatment device that holds or traps the grease, food solids, and oils discharged from a food service establishment prior to entering the sanitary sewer.  

 Who must have a grease interceptor? 

 All establishments preparing, handling, serving, or cleaning up food must have a grease interceptor that meets City of Arlington’s design and sizing specifications. For example, all restaurants, coffee shops, ice cream/snow cone shops, and child care facilities in Arlington must have a properly sized and designed grease interceptor.  

 Why are grease interceptors required?  

 Fats, oils, and grease (FOG) are present in almost all foods that we eat. In the same way that fat will clog your arteries, FOG in the sewer lines will clog sewer lines.  When this happens, the sewer will overflow, creating a danger to public health and the environment, and causing City of Arlington to pay thousands of dollars in fines to regulatory authorities and even more thousands of dollars for cleanup. The primary purpose of requiring wastewater pretreatment measures like grease interceptors is to prevent sanitary sewer overflows.  


The City of Arlington also spends millions of dollars every year to maintain our wastewater collection system; requiring properly sized and designed grease interceptors for all food establishments is an important preventative measure that will also protect the City’s wastewater collection system, reducing repair, maintenance, and replacement costs.   


Additionally, the City of Arlington is required to meet wastewater discharge standards by the Trinity River Authority (TRA), which treats our wastewater at the TRA Central Wastewater Treatment Plant. Requiring properly sized and designed grease interceptors is an attempt to meet the wastewater discharge standards for FOG (200 mg/L).  

 Can I use the existing grease interceptor on site?  

 If you are opening a food service establishment in an existing building, you may already have a grease interceptor that has been installed. Grease interceptors are just like any piece of equipment; over time, they begin to age and have issues. If the existing grease interceptor is not in good working condition, is grossly undersized by current standards, or plumbing fixtures are being added that would require a grease interceptor with a 

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larger capacity to be installed, you may need to replace the existing grease interceptor. Contact Water Resource Services at 817-459-5902 to determine if you will be able to use the existing grease interceptor.  

 What is a sample well and securing device?  

 Food service establishments must install a sample well and securing device in addition to the grease interceptor.   


The City of Arlington monitors wastewater samples from all food establishments, car washes, and certain permitted industrial users to make sure that the facility is not discharging abnormal wastewater that is harmful to the wastewater collection system or the wastewater treatment plant.  


The sample well is a type of manhole which City of Arlington will use to collect wastewater samples from the facility. The securing device is an eyebolt set in concrete inside of a valve box top cover; City or Arlington employees will clip their sampling equipment to this securing device while taking a wastewater sample. In most cases, the sample well will be plumbed to capture all wastewater discharges from the facility, including both grease and condensate waste.  

 What is the minimum size required for grease interceptors in Arlington?  

 In Arlington, grease interceptors are sized and designed in accordance with City of Arlington Ordinance #09-057 Industrial Waste and Water Pollution Control.  They are sized based on total potential flow from all plumbing fixtures and drains located in any food preparation, handling, serving, or clean up area. To summarize, the grease interceptor size is determined by the number and pipe size from these plumbing fixtures and drains; the minimum size is determined based on these numbers.  


Visit http://arlingtontx.gov/water/wrs.html to find City of Arlington’s Interceptor Sizing Spreadsheet or contact Water Resource Services at 817-459-5902 and ask to get in touch with the Analyst who does plan reviews.  

 What if I want to use a type of grease interceptor that is different from the design specifications of City of Arlington?  

 Contact Water Resource Services at 817-459-5902 and ask to get in touch with the Analyst who does plan reviews. Variations from the design specifications are evaluated on a case-by-case basis per City of Arlington ordinance.  

 What if I have more questions?  

 Contact Water Resource Services at 817-459-5902 and ask to get in touch with the Analyst who does plan reviews. Variations from the design specifications are evaluated on a case-by-case basis per City of Arlington ordinance.