Mesa's published restaurant FOG guide does not set a 25 percent trigger or 90 day limit. It calls for continuously efficient operation, a regular cleaning schedule and three years of records. Phoenix publishes numerical schedules. Confirm any facility-specific conditions with Mesa rather than assuming another city's numbers apply.
What Mesa does require
Mesa's official restaurant FOG guide cites City Code Title 8, Chapter 4, Sections 15(4), (8) and 22(D). It says the owner must maintain oil and grease interceptors to ensure "continuously efficient operation at all times." The same guide directs facilities to keep maintenance and service records on site for at least three years.
The city's restaurant FOG guide adds the practical side. It tells restaurants to "set up a regular cleaning schedule" with their maintenance vendor and to keep service records for a minimum of three years. It says not to "wait until your grease removal device is overflowing with waste to get it cleaned." It also says the recommended cleaning method is to pump out the entire device, including the residual waste after scraping and hosing down, and to have someone from your facility watch it happen.
The published guide does not state a percentage-full trigger or a fixed number of days. That does not rule out facility-specific conditions or an instruction from the city. The operating standard remains important: the device has to work, and you should keep records that show the maintenance performed.
Where the 25 percent and 90 day numbers come from
Phoenix. Its FOG manual says most interceptors stop working effectively when fats, oils and solids reach 25 percent of capacity, and requires a full cleaning above that. It sets hydromechanical interceptors at a full pump-out every 30 days, never more than 90 days without maintenance, and gravity interceptors at least every 3 months unless the Director grants a variance. We break that down in what the 25 percent rule means and how often to pump a grease trap.
Those numbers don't carry across the city line on their own. In Mesa, the test is the one in the code: is the device working at all times?
How to set your schedule in Mesa
- Start with Phoenix's numbers as a floor. Since Mesa gives you none, a monthly pump-out for a small trap and quarterly for a large interceptor is a defensible starting point. It's our suggestion, not a Mesa requirement.
- Adjust to what you actually make. A fryer-heavy kitchen fills a device faster than a sandwich shop. Have your pumper note how full the device is at each visit and move the date up or back.
- Never accept decanting. Mesa's guide says not to let the hauler decant wastewater from the truck back into the device or your sewer connection.
- Keep every invoice. Three years, on site, where an inspector can ask for them. See what to record in a grease trap log.
For the full code section, including who needs a device and how big it must be, read Mesa City Code 8-4-22.
If the line still backs up
A device that's pumped on time can still back up if the problem is downstream: a partial blockage, a sag, or grease that got past the outlet. HQ can run a camera through the kitchen line to see what's going on and clear it, and we give free estimates before any work starts. If you have questions about a specific backup, see commercial kitchen drain overflowing.