Phoenix City Code 28-12: Which businesses must install a grease or oil interceptor?

The section says interceptors "must be installed and operated by laundries, food service establishments, service stations, auto repair shops, carwashes, commissaries, and other facilities when the Director determines they are necessary for the proper handling of liquid wastes containing grease or oil in excessive amounts, or any flammable wastes, solids, or other harmful ingredients." Here is how the pieces work:

• Who is named: laundries, food service establishments, service stations, auto repair shops, car washes, commissaries and "other facilities." The list is examples, not a limit.
• Trigger: the Director finds an interceptor necessary. The Environmental Services Division of Water Services runs the program, and the plumbing code amendment ties interceptor approval to the Director of Water Services.
• What it handles: grease or oil in excessive amounts, flammable wastes, solids or other harmful ingredients.
• The next section (28-13): the interceptor must be a type and capacity the Director approves, from a published approved list, and it must be located where it stays free from obstructions and easy to reach for cleaning and inspection.

The city's FOG Best Management Practices Manual (June 2024) applies the rule to kitchens directly: "All Food Service Establishments that prepare food on site in the City of Phoenix are required to have a grease interceptor to prevent FOG from discharging to the city sewer."

• Interceptor: a device between your fixtures and the sewer that catches grease, oil or solids. Grease interceptors come as small indoor hydromechanical units (grease traps) or large outdoor gravity tanks.
• Food service establishment (FSE): the manual uses it for any business preparing food on site. Code 28-12 does not define it further.
• Commissary: the code lists it without a definition. Read it as a shared kitchen that supplies food trucks or carts. That is a reading, not the code's definition.
• Grease-bearing fixture: floor sinks, floor drains, mop sinks, prep, pot and pre-wash sinks, dishwashers and garbage disposals in the kitchen prep or wash area. Hand wash sinks do not count.

Every Phoenix business that fits the named types, whether you own the building or rent a suite. Maintenance is the user's job under the code, or the property owner's when several tenants share one interceptor. This does not automatically reach an office with a break room sink. Nothing in 28-12 lists it, and the Director's determination is what pulls a business in.

• Bakery with a three-compartment sink, prep sink and mop sink. Three grease-bearing fixtures, no dishwasher. A hydromechanical trap fits under the city's four-fixture limit.
• Same bakery adds a commercial dishwasher. The answer flips. The manual requires an outdoor gravity interceptor for any dishwasher or disposal, regardless of fixture count, and the smallest allowed is 500 gallons.
• Oil change shop with a floor drain. Section 28-12 names auto repair shops. Whether it needs a sand and oil interceptor is the Director's call. The city's approved list includes a Striem sand and oil separator marked "not for Food Service use."
• Ghost kitchen sharing one interceptor. Multi-user interceptors put maintenance on the property owner, not each tenant.

1. 1Count grease-bearing fixtures with the city's Food Service Establishment Fixture Count Worksheet (TRT 00227), which is Appendix C of the FOG manual.
2. 2Choose the device type from the counts above and pick a model from the city's approved list in Appendix A of the manual.
3. 3Submit plans for review. Any new or replacement interceptor goes through plan review with the Planning and Development Department. Call 602-495-0278 at least 24 hours ahead to book an Environmental Services inspector for their part of the review.
4. 4Have a licensed pumper clean it on the schedule in 28-15 and keep records for three years.
5. 5Questions on the program go to Environmental Services at 602-262-1859.

• "A grease trap under the sink is enough for any kitchen." Only up to four fixtures and no dishwasher or disposal.
• "Hand sinks count toward the four." The city's list of grease-bearing fixtures excludes hand wash sinks.
• "Enzymes or additives replace pumping." Section 28-15 prohibits using chemicals, enzymes, proteins, bacteria, solvents or emulsifiers to dissolve FOG in place of physical cleaning.
• "My landlord handles it." The code puts maintenance on the user, or the owner of a shared unit.

Inspections are unannounced. The manual says an inspector who finds a problem issues a requirement to clean, repair or replace with a time frame, that extensions can be granted in writing, and that the city can still take enforcement action if a sewer blockage or violation occurs during an extension.