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.

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 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.

In cities like New York, Los Angeles, Houston, and Chicago, FOG enforcement has tightened significantly in recent years as municipalities invest in sewer infrastructure and work to reduce sanitary sewer overflows. Many of these cities now require restaurants to maintain a FOG management plan on file and to use only licensed haulers for grease trap waste disposal.

Consequences of Non-Compliance

Grease trap violations carry some of the heaviest fines in restaurant regulation. Many jurisdictions impose penalties starting at $1,000 per violation per day, with repeat offenders facing fines of $10,000 or more. In extreme cases — particularly when a restaurant's FOG discharge causes a sewer overflow or environmental contamination — the fines can reach six figures and may include criminal liability for the business owner.

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 will shut down your restaurant immediately. The cost of emergency plumbing to clear a grease blockage typically runs $500 to $2,000 or more, plus the lost revenue from being closed.

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. Always check your local FOG ordinance for specific requirements, keep meticulous records, and train your kitchen staff on basic grease management practices. The cost of regular maintenance is a fraction of the cost of a violation or a sewer backup.