How Often Should a Grease Trap Be Pumped? Sizing, the 25 Percent Rule and Local Rules

"How often should we pump the trap?" is the question we hear most from kitchen managers, and the honest answer is: as often as your trap and your local rules require, and before it gets too full. Here is how to work out your schedule and keep proof that you followed it.

What the 25 percent rule means

A grease trap works because fats, oils and grease float, solids sink and water flows out. As the trap fills, there is less room for the water to slow down and separate. A widely used rule of thumb in the industry is simple: pump the trap before grease and solids make up one quarter of its depth. Past that point, grease starts to slip through to your lines and the sewer. Your local program's exact wording is what counts, so check it.

What sets your schedule

• Your permit and local rules. Atlanta kitchens answer to the city's grease management program. Charlotte kitchens answer to Charlotte Water's FlowFree program. Your permit or local policy comes first.
• Trap size. A small trap fills faster than a large one.
• How much grease your menu makes. Fried food, grilling and heavy dishwashing add more than a light menu.
• Seasons and volume. Holiday weeks and busy stretches fill a trap faster than slow ones.

If you are not sure which rules apply to you, check who sends your water bill and ask them for your requirements in writing.

How to tell your trap is getting too full

• Slow drains or water backing up in sinks
• Bad smells from floor drains or near the trap
• A thick crust at the surface when you open the lid
• Grease that shows up downstream of the trap

Do not wait for these signs. They mean the trap was overdue. See our grease trap service in Atlanta or our grease trap service in Charlotte.

What should happen at every pump out

1. The trap is fully pumped, not just skimmed.
2. The walls, baffles and lid are scraped and cleaned.
3. The outlet is checked for blockages.
4. You receive a record: date, company and what was removed, ideally with photos.

Keep the records at the kitchen

Inspectors want to see that the trap was serviced on schedule. Keep every manifest and photo report on site, not in an email inbox. For the specifics in your city, read what Atlanta's grease inspector checks or our Charlotte FlowFree guide.

Frequently Asked Questions