How often should a grease trap be pumped?
Most sewer authorities use the 25% rule: pump when fats, oils, grease and solids fill a quarter of the trap. In practice that's often every few weeks for small indoor traps and every 30 to 90 days for large interceptors.
Updated September 29, 2026
The 25% rule
Once grease and settled solids take up about 25% of the trap's depth, it stops separating grease well and starts letting it through to the sewer. That's why many local FOG programs set 25% as the point you must pump — and some set a fixed maximum interval as well.
Typical intervals
- Small indoor traps in busy kitchens: weekly or every two weeks
- Large in-ground interceptors: every 30 to 90 days, depending on size, menu and water flow
- Fryer-heavy and high-volume kitchens need service sooner than cafés and bakeries
Signs you're overdue
- Slow drains or backups at the sinks
- Grease or sewage smell near the trap
- Grease visible at the outlet or in the next manhole
- A notice or fine from your wastewater utility
Who decides
Your city or wastewater utility sets the rules for your trap — many have a fats, oils and grease (FOG) program with their own schedule and paperwork. Check with them.
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