INTERCEPTORS
Mesa City Code § 8-4-22
in effect8-4-22: - INTERCEPTORS
(A) Interceptors such as grease, oil, or sand shall be provided for laundries, restaurants, service stations, auto repair shops, carwashes, and other facilities when the City Manager or Water Resources Director determines that they are necessary for the proper handling of liquid wastes containing grease or oil in excessive amounts or any flammable wastes, sand, and other harmful ingredients.
(B) All interceptors shall be of a type and capacity approved by the City Manager or Water Resources Director and shall be located as to be readily and easily accessible for cleaning and inspection.
(C) Interceptors such as grease, oil, or sand shall be constructed of impervious materials capable of withstanding abrupt and extreme changes in temperature. They shall be of substantial construction, watertight, and equipped with easily removable covers. When bolted covers are required, they shall be gastight and watertight.
(D) Where installed, interceptors such as grease, oil, or sand shall be maintained by the owner, at the owner's expense, in continuously efficient operation at all times. The owner shall keep written records and documentation of all cleaning, repair, calibration, and maintenance required to demonstrate compliance with this Section. Records shall be kept at the facility for a minimum of three (3) years and shall be made available to the City Manager or Water Resources Director upon his request.
(E) The method for determining the size of traps or interceptors is the drainage fixture unit value. The minimum size for all interceptors is a capacity of five hundred (500) gallons and the maximum size for all interceptors is a capacity of twenty-five hundred (2,500) gallons. Interceptors must be constructed with at least two (2) chambers. Sizing for all traps is a minimum of a fifty (50) gallon per minute, one hundred (100) pound capacity with the flow control valve installed in a manner that provides access at all times. The appropriate size and traps is determined as follows:
(1) Interceptor Sizing. The interceptor shall be sized using the drainage fixture-unit value as defined in the following table. Using the drain outlet or trap size, these sizes are converted to discharge rates on the basis that one fixture-unit equals 7.5 gpm.
Fixture Outlet or Trap Size (Inches) | Drainage Fixture-Unit Value | gpm Equivalent
1¼ | 1 | 7.5
1½ | 2 | 15.0
2 | 3 | 22.0
2½ | 4 | 30.0
3 | 5 | 37.5
4 | 6 | 45.0
Dishwashers | Double Size
(2) Calculating Interceptor Size. The formula to calculate the size of the interceptor is:
a. Determine total fixture-unit value by multiplying fixture type count by drainage value;
b. Total all values;
c. Determine total flow by multiplying total value by flow rate of 3 gpm;
d. Multiply total flow by 12; and
e. Round up to the next nearest size interceptor.
(3) Requirements for Interceptors. The interceptor shall be:
a. A minimum of five hundred (500) gallon capacity, two (2) chamber concrete container (fiber glass and/or other type material must be approved by the City Manager or Water Resource Director or Designee);
b. When calculated to have a capacity of seven hundred fifty (750) gallons or more, the interceptor must have three (3) chambers, each with a manway;
c. Constructed with inlet piping with a ninety degree (90°) elbow and minimum of an eighteen (18) inch down spout;
d. Constructed with outlet piping with a tee connection and a threaded cover with a minimum of an eighteen (18) inch down spout;
e. Installed with a two (2) way clean-out within five (5) feet before and five (5) feet after the interceptor; and
f. Constructed with the appropriate traffic rated cover. The cover(s) must not be marked with any wording indicating it is owned by the City of Mesa.
(4) Grease Trap Installation and Sizing. Grease traps are allowed only when there are four (4) or fewer than four (4) fixtures used for food preparation. Any facility installing a dishwasher shall install a grease interceptor. For sizing a grease trap, a fixture means the entire unit, e.g., a three (3) compartment sink is considered one unit. Grease traps must be installed as follows:
a. A grease trap shall be installed whenever a three (3) compartment sink is required by Maricopa County;
b. The minimum size grease trap to be installed shall be rated no smaller than fifty (50) gallon-per-minute with a one hundred (100) pound grease capacity;
c. A flow restriction valve shall be installed upstream of the grease trap and vented properly. If placed below floor level the flow restriction valve must be installed in a manner which allows for inspection and maintenance; and
d. Except for domestic sources, users shall not install or replace equipment designed to convert garbage or solid waste into liquefied waste and introduce such waste into the POTW by means of a garbage grinder/disposal. Disposal of garbage and solid waste shall be disposed of as solid waste.
(Ord. No. 5959, § 2, 8-25-25)
Source: City of Mesa, Arizona, Mesa City Code and City Charter (Municode Library, library.municode.com)URL: https://library.municode.com/az/mesa/codes/code_of_ordinances?nodeId=COOR_TIT8HESAEN_CH4SASERE_8-4-22INFetched: 11/1/2026