Tempe City Code 27-22: grease traps, interceptors and the garbage disposal ban

Subsection (c) authorizes the Public Works Director to write Rules and Procedures for interceptors and traps and to require "nondomestic users, at the user's sole expense, to install, clean, maintain, repair and allow inspection of" lint traps, grease traps and interceptors, sand/oil interceptors, oil/water separators, hair traps and similar devices. It says interceptors and traps are not required for residential users. Devices must be installed under Chapter 8 (the plumbing code) and be the type and capacity set by the rules.

Subsection (d) bars the disposal: "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." Tempe's IPC 416.3 says the same thing: "Commercial food waste disposers are not allowed per the Public Works Director." IPC 1003.1 and 1003.3 add that the Director may attach extra conditions to any interceptor.

Subsection (f) covers food trucks. A mobile unit may discharge washwater upstream of a restaurant's device only with written authorization, and only if the device has the capacity and is being maintained. Section 27-15(c) makes tampering with a pretreatment device unlawful, including "discharge of waste into the pretreatment device from any source other than originally intended, or removal of a source of discharge from the pretreatment device as originally intended or designed."

• Grease trap: a small indoor device. Tempe's minimum is 50 gpm and 100 pounds of capacity.
• Grease interceptor: a larger tank outside the building. Tempe's FOG page gives a minimum of 500 gallons and a maximum of 2,500.
• Nondomestic user: any user that is not a home. It includes restaurants, schools and hospitals.
• The rules: the City's 2017 Rules and Procedures document. The code says it prevails if the two conflict. The rules use older subsection letters than the current code, so cite the code first.

Every non-residential user that prepares food or drink, plus vehicle repair and wet manufacturing, according to the Rules. The rules name restaurants, cafeterias, cafes, fast food outlets, schools, fraternal organizations, churches, hospitals, hotels and daycare centers. It does not require a device for a house.

A coffee shop with two sinks and a floor drain. Three fixtures, no dishwasher, minimal cooking. A 50/100 trap fits, subject to Public Works approval.

A new sit-down restaurant. A dishwasher alone forces an interceptor. Tempe's worked example sizes one this way: add the fixture-unit values, multiply by 3 gpm, multiply by 12, round up to the next available size. Their example comes to 23 units, 69 gpm and 828, rounded to 1,050 gallons. That is the city's example, not a promise for your kitchen.

The edge case: a new tenant in an old restaurant. The last tenant had a 750-gallon interceptor and it seems fine. The rules say any food service establishment getting a building permit for kitchen or plumbing changes is reviewed against the current criteria "regardless of whether the property has an existing device", and that no establishment is grandfathered for a prior occupant's device size or type.

1. 1Count the fixtures that will drain to the grease line: prep sinks, floor drains, floor sinks, mop sink, pot sink. Note any dishwasher.
2. 2Decide trap or interceptor using the table above. If you are between them, call Environmental Services at 480-350-2678.
3. 3Get written approval from the Public Works Director. The Rules say to obtain it by pulling a plumbing permit. Community Development takes permit questions at 480-350-8341.
4. 4Size the device with the city's fixture-unit method and keep the device out of any trash enclosure.
5. 5Remove any garbage disposal from the plan and route food waste to solid waste.
6. 6Choose a permitted hauler or look at the voluntary Tempe Grease Cooperative, covered on the Tempe FOG inspection page in this library.

• "The old tenant's device covers me." The Rules say there is no grandfathering for a prior occupant.
• "A trap is fine, we just added a dishwasher." Dishwashers may not connect to a trap.
• "A disposal is fine if it drains to the interceptor." Code says commercial disposers are not allowed, and 27-15(c) treats rerouting waste into a device as tampering.
• "27-22 sets the pumping schedule." The code text hands that to the Rules. The city's FOG page attributes monthly and quarterly service to 27-22.