Kitchen grease trap maintenance is a regulatory requirement and a practical necessity for every commercial kitchen. Grease traps (also called grease interceptors) prevent fats, oils, and grease (FOG) from entering the municipal sewer system, where they cause blockages, overflows, and environmental contamination. A neglected grease trap creates cascading problems — sewer backups, foul odors, pest attraction, health code violations, and potential fines. This guide covers how grease traps work, how to maintain them properly, and how to stay compliant with local regulations.
A grease trap is a plumbing device that slows the flow of wastewater from kitchen drains, allowing FOG to separate from the water by gravity. Because fats and oils are lighter than water, they float to the surface while heavier food solids settle to the bottom. The relatively clear water in the middle flows out to the sewer.
Passive grease traps (also called grease interceptors or gravity grease interceptors) are the most common type. They are typically concrete or fiberglass tanks buried outside the building, sized to handle the full flow from all kitchen drains. Capacity ranges from 750 to 2,000 gallons or more depending on the operation size. These units have no moving parts — they rely entirely on gravity separation and retention time.
Point-of-use grease traps (also called under-sink traps) are smaller units installed directly under individual sinks or dishwashers. They handle lower flow volumes (typically 10-50 GPM) and require more frequent cleaning due to their smaller capacity. Some jurisdictions require point-of-use traps in addition to exterior interceptors.
Automatic grease removal units (AGRUs) use heated water and mechanical skimming to remove accumulated grease on a timed schedule. They are more expensive but reduce manual cleaning frequency and maintain more consistent grease separation efficiency. Some jurisdictions accept AGRUs as equivalent to traditional interceptors when properly maintained.
The key measurement for grease trap effectiveness is retention time — how long wastewater stays in the trap before flowing to the sewer. Longer retention time allows more complete grease separation. A trap that is too small for your flow rate or that is not cleaned often enough has insufficient retention time, reducing its effectiveness and allowing grease to pass through to the sewer.
Grease trap cleaning frequency depends on your trap size, cooking volume, and menu type. The general rule is to clean before the trap reaches 25% of its total grease and solids capacity — beyond this point, separation efficiency drops significantly.
Interior point-of-use traps: Clean weekly or more frequently in high-volume operations. The procedure is straightforward:
Exterior interceptors: Clean on a schedule determined by your accumulation rate — typically every 1-3 months. Professional pumping service is required for large interceptors. The procedure includes:
Signs your grease trap needs immediate cleaning:
According to the EPA, FOG is the leading cause of sanitary sewer overflows in the United States. Municipalities worldwide have strengthened FOG regulations in response, making grease trap maintenance both an environmental and regulatory obligation.
Grease trap regulations vary by municipality, but common requirements include minimum cleaning frequency, record retention, and reporting.
Common regulatory requirements:
Documentation you must maintain:
Penalties for non-compliance can include fines (typically $100-$1,000 per violation per day), mandatory monitoring requirements, sewer surcharges, and in severe cases, connection to the sewer system being revoked — which effectively shuts down your kitchen.
Your grease trap maintenance program should be integrated with your broader kitchen maintenance schedule. See our restaurant kitchen equipment maintenance guide for a complete maintenance framework.
No matter how popular your restaurant is or how talented your chef is,
one food safety incident can destroy years of reputation overnight.
Your kitchen is the heart of food safety. Every piece of equipment, every temperature reading, every cleaning rotation either protects your customers or puts them at risk. Kitchen management isn't just about efficiency — it's about safety.
Most food businesses manage safety with paper checklists — or worse, memory.
The businesses that thrive are the ones that make safety visible to their customers.
Track your kitchen temperatures digitally (FREE):
Already managing food safety? Show your customers with a MmowW Safety Badge:
安全で、愛される。 Loved for Safety.
Use our free tool to check your food business compliance instantly.
Try it free →An undersized grease trap fails to separate grease effectively. An oversized trap wastes money on installation and may still require the same cleaning frequency. Correct sizing is based on your wastewater flow rate and the type of cooking you do.
Flow rate calculation starts with the fixtures connected to the trap. Each fixture has a rated drainage fixture unit (DFU) value:
Your grease trap must handle the total DFU of all connected fixtures simultaneously. The Plumbing and Drainage Institute (PDI) standard PDI-G101 provides sizing tables that convert total DFU to required trap capacity in gallons per minute (GPM).
Menu type affects accumulation rate. A fried chicken restaurant generates far more grease than a sushi bar, even with the same flow rate. Operations heavy in fried foods, grilled meats, and butter-based cooking need either larger traps or more frequent cleaning. Some jurisdictions require grease production audits for high-FOG operations.
Pre-treatment devices like drain screens, food solids interceptors, and dishwasher drain baskets reduce the load on your grease trap by capturing food solids before they enter the trap. These devices are inexpensive and dramatically extend cleaning intervals.
Even well-maintained grease traps develop issues. Early identification prevents minor problems from becoming major plumbing emergencies.
Problem: Persistent odors despite regular cleaning.
Cause: Bacterial decomposition of organic matter in the trap or drain lines. Solution: Increase cleaning frequency. Apply enzyme-based drain treatments between cleanings to break down organic buildup. Check that the trap lid seals properly — a poor seal allows odors to escape even when the trap is clean.
Problem: Slow drainage after recent cleaning.
Cause: Obstruction in the inlet or outlet pipes rather than in the trap itself. Solution: Have a plumber inspect and clean the connecting pipes. Grease can accumulate in elbows, tees, and horizontal runs between fixtures and the trap.
Problem: Grease passing through the trap to the sewer.
Cause: Trap is too small for the flow rate, baffles are damaged or missing, or the trap is not being cleaned before reaching 25% capacity. Solution: Verify trap sizing, inspect and replace damaged baffles, and increase cleaning frequency.
Problem: Water backing up into the kitchen.
Cause: Complete blockage in the trap, outlet pipe, or downstream sewer connection. Solution: Emergency pumping and professional plumbing service. Do not attempt to clear a complete blockage with chemicals — they can damage the trap and are ineffective on grease blockages.
For related kitchen infrastructure topics, see our commercial kitchen cleaning protocols.
How often should a commercial kitchen grease trap be cleaned?
Clean before the trap reaches 25% grease and solids capacity. For most operations, this means monthly to quarterly for exterior interceptors and weekly for under-sink traps. High-volume frying operations may need more frequent service. Your local sewer authority may specify minimum cleaning frequency.
Can I clean my own grease trap?
Small under-sink traps can be cleaned by kitchen staff as part of routine maintenance. Large exterior interceptors require professional pumping due to volume, disposal regulations, and the need for proper waste manifests. In most jurisdictions, grease waste must be transported by licensed haulers to approved disposal facilities.
What happens to grease waste after it is pumped?
Licensed haulers transport grease waste to rendering facilities, wastewater treatment plants, or anaerobic digesters where it is processed. Some facilities convert FOG into biodiesel or biogas. Illegal dumping of grease waste carries significant penalties.
Do enzymes or bacteria additives eliminate the need for grease trap cleaning?
No. Enzyme and bacteria products can supplement regular cleaning by reducing grease accumulation between pump-outs, but they do not replace physical removal of accumulated grease and solids. Some municipalities prohibit certain additives because they can cause grease to pass through the trap into the sewer system.
Grease trap maintenance is not glamorous, but it is one of the most consequential maintenance tasks in your kitchen. A well-maintained trap prevents sewer backups, eliminates odor complaints, avoids regulatory fines, and reduces pest attraction — all of which protect your business and your customers.
Review your current cleaning schedule against the guidelines in this article. If you cannot show a health inspector dated pump-out records for the past year, schedule a cleaning now and start building your maintenance record.
Integrate temperature and safety tracking into your routine (FREE):
安全で、愛される。 Loved for Safety.
Try it free — no signup required
Open the free tool →MmowW Food integrates compliance tools, documentation, and team management in one place.
Start 14-Day Free Trial →No credit card required. From $29.99/month.
Loved for Safety.