How Often Does a Restaurant Grease Interceptor Need to Be Pumped in Phoenix and Mesa?

What are Phoenix's grease interceptor pumping rules?

Phoenix sets these rules under City Code Chapter 28 (Sewers) and explains them in its Fats, Oils and Greases (FOG) Best Management Practices manual. Every Phoenix food service establishment that prepares food on site must have a grease interceptor.

The schedule depends on the type of interceptor. These are minimums; the 25 percent rule can require cleaning sooner.

• Hydromechanical interceptors (grease traps): fully pumped out and cleaned every 30 days unless the Director grants a variance, and never more than 90 days without maintenance.
• Gravity interceptors: fully pumped out and cleaned at least once every 3 months unless the Director grants a variance.
• Any interceptor: a full cleaning is required when fats, oils, grease and solids take up more than 25 percent of its capacity.
• Cleaning must be done by a licensed pumper, and the interceptor must be left completely empty.
• Maintenance records, including pumping invoices, must be kept at the facility for three years and shown to the city on request.

Do you have a grease trap or a gravity interceptor?

A hydromechanical interceptor, usually called a grease trap, is small and typically installed indoors. Phoenix approves them for kitchens with up to four plumbing fixtures, such as a three-compartment sink, a prep sink and a mop sink. Garbage disposals and dishwashers may not drain to one.

A gravity grease interceptor is a much larger tank installed outdoors. Phoenix requires one for establishments with more than four plumbing fixtures and for any kitchen with a garbage disposal or dishwasher, regardless of fixture count. The smallest gravity interceptor the city allows is 500 gallons.

The City of Mesa explains that an interceptor slows wastewater down so grease floats and solids sink. Phoenix notes that most interceptors stop separating effectively once grease and solids fill a quarter of the device, which is why pumping frequency matters.

What does the 25 percent rule mean in practice?

The 30-day and 3-month schedules are a floor, not a target. A busy kitchen with fryers, heavy dish volume or long hours can reach 25 percent well before its scheduled pump-out.

Phoenix advises new facilities to monitor the interceptor with their pumping company or a city inspector and adjust the frequency to the grease that actually builds up. Ask your pumper to note the grease and solids level on every service ticket so you can tell whether your interval is right.

Phoenix also recommends that someone from the business watch each cleaning to confirm the interceptor is fully emptied and to look for damaged or missing parts. Mesa gives similar advice and adds that, while the device is empty, you should check that the inlet and outlet have down-turned elbows or tees in good condition.

What does the City of Mesa require?

Mesa's Water Resources Department says grease removal devices are required during construction of most food service establishments. Under City Code Title 8, Chapter 4, the owner must maintain every oil and grease interceptor so it operates efficiently at all times. Mesa's restaurant guidance recommends a regular cleaning schedule with your maintenance vendor rather than publishing a single fixed number of days, so ask the city's industrial pretreatment staff what interval applies to your kitchen.

Mesa's recommended cleaning method is to pump out the entire device, remove all of its contents, and remove the residual waste after scraping or hosing down the walls. The city also lists several things to avoid.

• Keep maintenance and service records at the facility for at least three years.
• Do not let the waste hauler pour wastewater from the truck back into the interceptor or the sewer connection.
• Do not wait until the device is overflowing to have it cleaned.
• Do not use drain-opening chemicals on a clogged drain; have a plumber evaluate it.

What about Tempe, Chandler, Gilbert, Scottsdale and other Valley cities?

Each city runs its own sewer system and pretreatment program, so do not assume the Phoenix schedule applies everywhere. If your kitchen is outside Phoenix or Mesa, check with your city's pretreatment or FOG program for the required interval, the recordkeeping rules and whether a permit applies. Keeping every pumping ticket for at least three years is a sensible habit wherever you operate.

Can enzymes or bacteria treatments replace pumping?

Not in Phoenix. The city prohibits using chemicals, enzymes, proteins, bacteria, grease solvents or emulsifiers to temporarily dissolve fats, oils and grease. In other words, an additive does not count as cleaning. Phoenix also prohibits the pumper from putting removed water or material back into the interceptor or the sewer; everything removed goes to a licensed waste disposal facility.

Which kitchen habits slow down how fast the interceptor fills?

Phoenix points out that the less grease reaches the interceptor, the less often it needs pumping. The city recommends these practices for every business with a kitchen.

• Train employees on grease handling and document the training.
• Scrape or dry-wipe food and grease from pots, pans, fryers, utensils, screens and mats into the trash before washing.
• Put removable screens on kitchen drains and clean them often.
• Recycle used cooking oil through a collection company instead of pouring it out.
• Clean grease and oil spills with absorbent material before mopping.
• Keep the tallow bin and dumpster area clean, with lids closed, so grease is not washed into storm drains when it rains.

What happens during a Phoenix FOG inspection?

Phoenix commercial inspections are unannounced so inspectors can see how the kitchen runs day to day. The inspector reviews your interceptor maintenance records, checks the interceptor for missing parts or deterioration and checks how much grease is in it, counts the grease-bearing fixtures to confirm the interceptor is sized correctly, and looks at the tallow bin and trash area.

If something needs correcting, the inspector issues a requirement with a time frame to clean, repair or replace it.

Where does interceptor pumping end and drain line cleaning begin?

Pumping empties the interceptor. It does not clean grease that has already coated the kitchen branch lines upstream or the building sewer downstream. If floor sinks back up between pump-outs, drains slow down right after service, or the interceptor fills unusually fast, the problem may be in the piping rather than the tank.

For those lines we look at access points, the pipe material and the history of the problem, then recommend cleaning such as hydro jetting and a maintenance interval that fits the kitchen's volume. We confirm the cause and the price before work begins and document what we found so it can go in your maintenance file next to the pumping records.

Common questions

Sources

• City of Phoenix Water Services: FOG Best Management Practices for Food Service Establishments (June 2024)
• City of Phoenix: Commercial Inspection and Fat, Oils, and Grease
• City of Mesa Water Resources: Restaurant Facilities FOG guidance
• City of Mesa: How a Grease Interceptor Works
• City of Mesa: Industrial Pretreatment