Who sizes a restaurant grease interceptor in Maricopa County: the county or the city?

The county's guide to plan review for food establishments says, under Grease Interceptors/Grease Traps: "Local municipalities determine the number and size of grease traps, grease interceptors or catch basins." If one is required, it says, refer to the local municipality for the installation requirements.

Four other lines from the same guide fill in the picture:

• County land. "If the establishment is located outside a municipality on county land, contact the Water & Waste Division for Independent Sewage Disposal Systems (ISDS) inspections or current code requirements."
• Access. If a trap is installed, it "must be properly spaced so they are easily accessible for servicing and cleaning." An above-ground trap near a wall needs the gap trimmed and sealed.
• Equipment section wording. The equipment list says "Local municipality or County adopted plumbing code requirements determine the number and size of grease traps, grease interceptors, or catch basins."
• A bulk grease recycling system is not a trap. The guide's note says so in as many words.

For plumbing in unincorporated areas, the county adopted the 2018 International Plumbing Code with its Local Additions and Addenda. Tab I amends section 1003.3: "Grease interceptors shall comply with the requirements of Sections 1003.3.1 through 1003.3.8 and Maricopa County Environmental Services requirements." The county does not publish the ICC code text, so the IPC sections themselves are not quoted here.

• Local municipality. The city or town the building sits in. For a building on unincorporated county land, there is no city, which is why the guide points to the county Water & Waste Division.
• Catch basin. The guide lists it alongside traps and interceptors without defining it.
• Nonhazardous liquid waste. The county code's definition includes "grease trap wastes," which puts grease pumping under the county's hauler permit rule.

A restaurant plan has two layers here: the plumbing code that sizes the device, and the county health plan review that expects it to be accessible. Which plumbing code applies depends on where the building sits.

This does not apply if your building is in a city that has its own interceptor ordinance and sizing rules. In that case the city's code controls the size, and the county guide is telling you to go there.

A restaurant in a Valley city. The owner searches the county site for an interceptor size and finds nothing. That is because the guide sends the question to the city. In Mesa, for example, the city code states a 500 to 2,500 gallon range, as the comparison table shows. The county plan reviewer then checks only that the unit is accessible and sealed at the wall.

A roadside restaurant on county land. No city code applies. The owner calls the Water & Waste Division, whose number is on the county guide, and designs to IPC 1003.3 plus the Environmental Services requirements named in the Local Additions.

The edge case. A small cafe installs a self-contained bulk grease recycling system and assumes that satisfies the grease rule. The guide's own note says it is not a grease trap, so the city or county sizing rule still has to be answered.

1. 1Confirm whether the address is inside a city or on unincorporated county land. Your tax record or the city's service area map settles that.
2. 2Inside a city, ask that city's plan review desk for its interceptor sizing rule and design to it.
3. 3On county land, contact the Water & Waste Division. The county guide lists (602) 506-6666 and (602) 372-1364 for well and septic questions.
4. 4Show the trap or interceptor on the plan set with enough clear space around it for servicing, and seal any gap against a wall.
5. 5For pumping, use a hauler with a county nonhazardous liquid waste permit. The MCEHC says no person shall "remove, store, transport, or dispose of any Nonhazardous Liquid Wastes" without a permit, and the vehicle must be approved by the Department. Pumping is a separate trade from interceptor repair or inspection, and the pumper goes first.

• Myth: The county sized my interceptor. The guide says local municipalities determine number and size.
• Myth: Any truck can haul it. The county's code requires a permit to remove, store, transport or dispose of nonhazardous liquid waste, and its definition names grease trap wastes. The posted fee is $175.00 per vehicle.
• Myth: The model code answers it by itself. In the unincorporated county, IPC 1003.3 is amended to add county Environmental Services requirements.
• Myth: Crowding the unit against a wall is fine. The guide says traps must be spaced so they are easily accessible for servicing and cleaning.