The Complete Grease Trap Maintenance Guide for Restaurants

March 7, 2026

Grease traps are one of those things restaurant owners don't think about until something goes wrong. But a neglected grease trap can lead to sewage backups, foul odors in the dining room, health code violations, and expensive emergency plumbing calls. This guide covers everything you need to know to keep your grease trap maintained, compliant, and cost-effective.

What is a grease trap and why does it matter?

A grease trap (also called a grease interceptor) is a plumbing device that captures fats, oils, and grease (FOG) before they enter the municipal sewer system. FOG solidifies as it cools, and without a trap, it accumulates in sewer lines causing blockages that are expensive to clear and can result in raw sewage backups.

Most municipalities require commercial kitchens to have grease traps installed and properly maintained. The specifics vary by city, but the consequences of non-compliance are consistent: fines, mandatory shutdowns, and liability for sewer damage.

How often should you clean your grease trap?

The standard rule of thumb is the 25% rule: your grease trap should be cleaned when FOG and solid content reaches 25% of the trap's capacity. Beyond this point, the trap's efficiency drops significantly and you risk grease passing through to the sewer line.

In practice, how quickly you hit 25% depends on several factors:

• Volume of cooking: A high-volume fry kitchen fills up much faster than a salad-focused cafe.
• Trap size: Under-sink interceptors (20–100 gallons) fill faster than large in-ground traps (500–2,000 gallons).
• Menu: Kitchens that do a lot of frying, grilling, or sautéing produce more FOG.
• Pre-cleaning practices: Scraping plates and dry-wiping pans before washing reduces FOG entering the trap.

For most restaurants with under-sink traps, cleaning frequency ranges from weekly to monthly. The problem with fixed schedules is that they're either too frequent (wasting money) or not frequent enough (risking overflow). This is exactly why data-driven monitoring is valuable.

Grease trap compliance requirements

Compliance requirements vary by municipality, but common elements include:

• Maintaining FOG levels below 25% of trap capacity
• Keeping maintenance logs with dates, hauler information, and volumes pumped
• Using a licensed grease hauler for disposal
• Allowing periodic inspections by the local water authority
• Having a properly sized trap for your kitchen's flow rate

Fines for non-compliance vary widely. Some cities issue warnings first; others start at $500–$1,000 per violation and escalate from there. In severe cases, repeated violations can lead to mandatory closure until the issue is resolved.

What a grease trap cleaning involves

Professional grease trap cleaning typically follows these steps:

1. The technician removes the trap lid and measures the current FOG layer thickness
2. Standing water is pumped out first
3. FOG and settled solids are vacuumed out
4. The trap interior, baffles, and inlet/outlet pipes are scraped and cleaned
5. The trap is reassembled and filled with clean water
6. The hauler provides a manifest documenting the service

A typical pump-out for an under-sink interceptor costs $150–$400 depending on your location and the trap size. Emergency calls after-hours or for overflow situations can be two to three times higher.

Tips to reduce grease trap maintenance costs

• Train your staff: Make sure everyone knows to scrape plates into the trash, never pour oil down the drain, and dry-wipe greasy pans before washing.
• Use strainer baskets: Simple drain strainers catch food solids before they enter the trap, reducing the solid layer buildup.
• Monitor fill levels: Instead of pumping on a fixed schedule, know when your trap actually needs service. This is where sensor-based monitoring like FOGhorn comes in — you only pay for pump-outs when the data says it's time.
• Keep records: Good maintenance logs help you spot patterns (seasonal changes in grease production, for example) and optimize your schedule.

The future: data-driven grease trap management

The restaurant industry is increasingly moving toward data-driven operations, and grease trap management is no exception. Non-invasive ultrasonic sensors like FOGhorn mount on the outside of plastic grease traps and continuously monitor FOG levels without any contact with grease, sending alerts when service is actually needed. This eliminates both the risk of overflow (from waiting too long) and the waste of unnecessary pump-outs (from servicing too early).

For restaurant operators managing multiple locations, remote monitoring also means visibility across all your traps from a single dashboard, without relying on staff to remember to check.