Grease Trap Cleaning Requirements: What Every Restaurant Owner Needs to Know

What Is a Grease Trap and Why Is It Regulated?

A grease trap (also called a grease interceptor) is a plumbing device designed to catch fats, oils, and grease (FOG) before they enter the municipal sewer system. Every commercial kitchen that prepares food generates FOG, and when it enters the sewer, it solidifies, builds up on pipe walls, and eventually causes blockages. These blockages can lead to raw sewage overflows — a public health hazard that municipalities take very seriously. In its report to Congress on sanitary sewer overflows, the EPA found that grease was the most common cause of reported sewer blockages — 47% of them — and blockages are a leading cause of overflows.

This is why virtually every city and county in the United States requires commercial kitchens to have a properly sized grease trap that is cleaned on a regular schedule. The specifics vary by jurisdiction, but the underlying principle is universal: your FOG stays out of the public sewer system, or you face consequences.

The 25% Rule: The Most Common Standard

The most widely adopted standard for grease trap maintenance is the “25% rule” — your grease trap must be pumped out before the combined total of fats, oils, grease, and settled solids exceeds 25% of the trap's total capacity. Once the FOG layer and solids reach one-quarter of the trap's volume, the device can no longer effectively separate grease from wastewater.

In practical terms, this means most restaurant grease traps need pumping every one to three months, depending on the trap size, cooking volume, and the types of food being prepared. A busy restaurant doing heavy frying may hit 25% capacity in as little as two weeks, while a lower-volume operation with a large interceptor might go three months between cleanings.

Indoor Grease Traps vs. Outdoor Grease Interceptors

There are two main types of grease management devices, and the cleaning requirements differ significantly between them. Indoor grease traps (also called point-of-use or under-sink traps) are smaller units, typically 20 to 100 gallons, installed near the source of FOG discharge. Because of their small size, they fill up quickly and generally need cleaning every two to four weeks for high-volume kitchens.

Outdoor grease interceptors are larger underground tanks, typically 500 to 2,000 gallons or more, installed outside the building. These serve the entire kitchen and, because of their larger capacity, can go longer between pumpings — often 60 to 90 days. However, they require a licensed pumping truck to service and are more expensive per cleaning.

FOG Regulations by Major Metro Areas

While the 25% rule is widely adopted, specific FOG regulations vary by jurisdiction. Many municipalities have their own FOG pretreatment programs that impose additional requirements beyond the basic cleaning schedule. These may include mandatory FOG disposal manifests, best management practices for kitchen staff, and regular reporting to the local sewer authority.

Here is how the eight cities we cover handle it (checked November 2026):

Consequences of Non-Compliance

Grease violations can be expensive. Federal pretreatment rules require local sewer authorities to be able to seek penalties of at least $1,000 per day for each violation, and many go further: New York City’s maximum is $10,000 per day, per violation, while Houston issues citations of $250 to $2,000 per violation. Authorities can also charge you for clearing a blockage or cleaning up an overflow your grease caused.

Beyond fines, a neglected grease trap creates immediate operational problems. A full trap means FOG passes through into the sewer line, where it hardens and creates blockages. This can cause sewage to back up into your kitchen — a health code emergency that can close you until it is cleaned up — on top of the emergency plumbing bill and the lost trade.

Best Practices for Grease Trap Maintenance

Staying compliant with grease trap regulations is mostly about establishing a routine and sticking to it. Schedule your pump-outs in advance with a reliable provider and set calendar reminders. Keep all service receipts, manifests, and pump-out reports in an organized file — inspectors will ask for these. Train kitchen staff on basic FOG management: scrape plates before washing, never pour oil or grease down drains, and use strainers on all drain openings.

Between professional cleanings, monitor your trap regularly. Most indoor traps have a visible inspection point. If you can see a thick layer of grease forming on top, it is time to call your provider regardless of where you are in the schedule. Proactive maintenance is always cheaper than emergency service.

Key Takeaways

The 25% rule is the most common standard: pump your grease trap before FOG and solids exceed one-quarter of the trap's capacity. For most busy restaurants with indoor traps, this means monthly service; outdoor interceptors can often go two to three months. Many cities also set a hard limit — Houston and Dallas require pumping at least every 90 days, Phoenix every three months for gravity interceptors and every 30 days for indoor units. Check your local rules, keep every manifest, and train your kitchen staff on basic grease management. The cost of regular maintenance is a fraction of the cost of a violation or a sewer backup.