Grease Trap Cleaning

A grease trap (also called a grease interceptor) is a plumbing device installed between your commercial kitchen drains and the septic system or sewer connection. It works by exploiting a simple physical principle: fats, oils, and grease are lighter than water. The trap slows the flow of wastewater from your kitchen, giving FOG time to float to the surface and solidify into a grease cap, while heavier food particles settle to the bottom as sediment. The relatively clean water in the middle layer flows out to your septic system or sewer.

Over time, the accumulated grease cap on top and sediment layer on the bottom reduce the trap's effective capacity — the middle zone of clean water gets smaller and smaller. When grease and solids take up too much space, FOG starts passing through with the outgoing water, defeating the trap's entire purpose. In a septic system, escaped FOG coats the drain field soil and creates a waterproof barrier that prevents effluent absorption — essentially smothering the field. In a sewer-connected system, FOG accumulates in municipal pipes and contributes to sewer blockages that affect the entire neighborhood.

Grease trap cleaning removes these accumulated layers using vacuum equipment similar to septic pumping trucks. The entire contents — grease cap, water, and sediment — are pumped out, the trap interior is scraped and rinsed, and the trap is refilled with clean water to re-establish proper operating conditions.

The general rule governing grease trap cleaning frequency is the 25% rule: clean your trap before the combined grease cap and sediment layers reach 25% of the trap's total depth. This rule is codified in most municipal ordinances and health codes, and exceeding it constitutes a violation in most jurisdictions regardless of whether any overflow has actually occurred.

For practical scheduling, the 25% threshold translates to different calendar intervals depending on your operation's volume and the trap size. High-volume restaurants with heavy frying operations (fried chicken, fish and chips, commercial fryers running all day) typically reach 25% in 3 to 4 weeks and need monthly cleaning. Standard full-service restaurants usually operate on a 6 to 8 week cleaning cycle. Low-volume establishments — cafes, delis, bakeries, small offices with a kitchen — may go 2 to 3 months between cleanings. Your local health code likely specifies a maximum interval regardless of accumulation level — in most jurisdictions, grease traps must be cleaned at least every 90 days even if the 25% threshold hasn't been reached.

Grease trap cleaning takes 30 minutes to 2 hours depending on trap size, accessibility, and the degree of buildup. Small under-sink traps (20 to 50 gallons) can be cleaned in 30 to 45 minutes with portable equipment. Standard in-ground traps (100 to 500 gallons) typically take 45 minutes to 1.5 hours. Large interceptors (500+ gallons) may require 1 to 2 hours with a full-size vacuum truck.

Schedule service during off-peak hours to minimize disruption to kitchen operations. Most grease trap companies offer early morning (before the kitchen opens), late evening (after close), or overnight service for exactly this reason. During cleaning, the kitchen drains connected to the trap cannot be used — plan your cleaning window so it doesn't overlap with prep or service periods.

Expect to pay $150 to $300 for small traps (under 100 gallons) and $300 to $500 for large in-ground interceptors per visit. Service contracts with scheduled recurring cleanings — monthly, bi-monthly, or quarterly — typically offer a 10 to 20% discount per visit compared to on-demand scheduling, and they eliminate the risk of missing a cleaning interval and falling out of compliance.

The technician should leave the area clean, provide the service receipt with measurements and trap condition notes, and provide the waste manifest documenting disposal. Before the crew leaves, confirm the next scheduled cleaning date if you're on a recurring service plan. Ask about automated monitoring options — some modern traps can be equipped with sensors that measure grease accumulation in real time and alert you when cleaning is needed, replacing the guesswork of calendar-based scheduling with data-driven maintenance.

Grease trap cleaning costs are driven by trap size, cleaning frequency, and accessibility. Understanding these factors helps you budget for this recurring operational expense and evaluate whether quotes are reasonable.

Cleaning frequency affects your annual cost substantially. A high-volume restaurant paying $400 per monthly cleaning spends $4,800 per year on grease trap maintenance. A low-volume cafe paying $200 per quarterly cleaning spends $800 per year. The cost per cleaning is relatively fixed, so the frequency is the controllable variable — and frequency is driven by the ratio of your FOG production to your trap's capacity. A larger trap costs more per cleaning but needs cleaning less often, which can reduce annual costs while providing a larger compliance buffer.

Emergency cleaning (after-hours, same-day response for overflows) costs 50 to 100% more than scheduled service. A $400 regular cleaning becomes $600 to $800 when a Saturday night grease backup forces an emergency call. Maintaining a regular cleaning schedule eliminates emergency calls in virtually all cases.

Disposal fees are typically included in the cleaning price but are worth understanding. Grease trap waste must be transported to approved rendering facilities or treatment plants — the waste manifest documents this chain of custody. In areas with limited disposal options, the disposal component of the cleaning fee may be higher.

For grease trap cleaning, reliability and compliance documentation matter more than finding the lowest per-visit price. A missed cleaning that results in a health code violation costs far more than any per-visit savings.

Check references from other food service operators in your area — restaurant managers and commercial kitchen operators can speak to reliability, punctuality, thoroughness, and documentation quality better than general online reviews. SepticTankHub lists grease trap service providers with capabilities, service areas, and customer feedback to help you compare options.