Grease trap guides
Grease traps are regulated by your city, not by a national standard, and the rules differ a lot from one city to the next. What doesn’t change is the 25% rule, and the difference between a small indoor trap and a large outdoor interceptor.
Guides
- Grease traps · CalculatorGrease trap sizing calculatorSize a grease trap from your sinks (flow rate in gpm) or a grease interceptor from your seats (gallons), using the fixture method and the Uniform Plumbing Code formula. Shows every step, plus the typical pumping cost for that size.
- Grease traps · PumpingHow often should a grease trap be pumped?Grease trap maintenance in full: the 25% rule, the pumping intervals Phoenix, San Jose and other cities write into law, a daily-to-quarterly maintenance checklist, what makes a trap fill faster, and the records you must keep.
- Grease traps · CostsWhat does grease trap pumping cost?Grease trap and interceptor pumping prices by size from the City of Tempe’s published 2025 price list, the add-on fees that change the bill, what a year of pumping costs, and why a neglected trap costs more.
Trap or interceptor?
| Grease trap | Grease interceptor | |
|---|---|---|
| Also called | Hydromechanical interceptor | Gravity interceptor |
| Where | Indoors, near the sink | Outdoors, underground |
| Who cleans it | Often staff, weekly to monthly | A pumping company with a vacuum truck, quarterly or longer |
Who sets the rules
Grease traps protect the public sewer, so your city's sewer utility or FOG (fats, oils and grease) program sets the requirements: how often to pump, what records to keep, and what you may not put down the drain. Intervals range widely — from every 2 weeks for indoor traps in Pleasanton, California to once a year for outdoor interceptors in Phoenix. The details, city by city, are in how often should a grease trap be pumped.
The three rules that apply nearly everywhere
- Pump at 25%. When grease and solids reach a quarter of the liquid depth, the trap must be pumped, whatever the schedule says.
- Pump it all. A complete pump-out, not skimming the top or returning water to the tank.
- Keep the paperwork. Two to three years of pumping records on site is typical.
Sizing
Indoor traps are sized by flow from the sinks that drain to them; outdoor interceptors by volume from seats, service and hours. The grease trap sizing calculator does both and shows its working.
What it costs
The City of Tempe publishes its grease cooperative's prices: $118 for a standard indoor trap, $270 to pump a 1,000-gallon interceptor, roughly 25 cents a gallon for larger tanks. Size-by-size prices and the add-on fees are in what does grease trap pumping cost.