Kitchen Grease Trap Maintenance: Codes, Cleaning Schedules, and Compliance

A grease trap is not optional equipment. It is a legally mandated infrastructure component in virtually every jurisdiction that governs commercial food service. Ignore it, and you are accumulating both a plumbing failure and a compliance violation simultaneously.

Fats, oils, and grease — collectively called FOG in the regulatory world — are a byproduct of commercial cooking that cannot go directly into municipal sewer systems. When FOG enters the sewer, it cools, solidifies, and accumulates on pipe walls. Over time it reduces pipe diameter, causes blockages, and triggers sanitary sewer overflows that contaminate waterways and create public health hazards. Municipalities have spent decades strengthening FOG management regulations, and the trend is toward stricter enforcement, not more flexibility.

What the Code Requires

According to the EazyGrease grease trap guidelines, grease traps and interceptors are mandated by the International Plumbing Code (IPC), Chapter 10. While the IPC is a model code — meaning local jurisdictions adopt and adapt it — grease management requirements exist in virtually every state, county, and municipal code governing food service operations.

The two types of devices the code recognizes serve different operational scales:

Point-of-use grease traps are smaller units installed directly under or near sinks and dishwashers. They handle lower volumes of wastewater and are designed for smaller kitchens or specific fixture connections. Because they are smaller and handle a higher concentration of FOG relative to their capacity, they require more frequent cleaning — typically monthly at minimum, or when grease reaches 50 percent of the trap capacity.

In-ground grease interceptors are larger units — typically 500 gallons or more — installed below grade, either inside or outside the building. They handle the entire kitchen’s wastewater flow and are pumped by professional service companies. According to the EazyGrease guide, large interceptors require cleaning at minimum every three months, with the actual trigger being when grease accumulation reaches 25 percent of the total liquid volume in the unit.

The 25 percent rule is the practical operating standard: you should not wait for the quarterly calendar date if grease is building up faster than expected. The level should be checked monthly regardless of cleaning frequency.

How a Grease Trap Works

According to the commercial kitchen plumbing and grease trap guide, the operating principle is straightforward passive separation. Wastewater from kitchen sinks and dishwashers flows into the trap. As the water cools inside the trap, FOG — which is less dense than water — floats to the surface. Heavier solids settle to the bottom. The clarified water in the middle layer exits through an outlet pipe into the municipal sewer system.

No energy input, no moving parts. The trap works as long as it is not overloaded and is cleaned before accumulation reaches the threshold that disrupts the separation process.

When a trap is overloaded or neglected:

• FOG bypasses the separation layer and exits through the outlet pipe
• The grease enters the municipal sewer
• Eventually, it either causes a blockage in your building’s sewer lateral or contributes to a larger system blockage
• Both outcomes generate emergency plumbing calls, potential fines from the sewer authority, and possible health code violations

Sizing Requirements

Getting the size right during installation matters more than most operators realize. According to the commercial kitchen plumbing guide, sizing follows established formulas based on:

• The number of sinks, commercial dishwashers, and other fixtures connected to the trap
• The maximum flow rate measured in gallons per minute (GPM) from connected fixtures
• The volume of FOG the kitchen generates based on cooking method and menu type

The Plumbing and Drainage Institute (PDI) establishes standard sizing calculations that local jurisdictions adopt. Facilities using commercial dishwashers typically require a minimum 500-gallon liquid holding capacity interceptor. Flow rate specifications generally range from a minimum of 20 GPM to a maximum of 55 GPM for in-ground interceptors, though local requirements vary.

Undersizing is the more common error. An undersized trap fills rapidly, requires frequent pumping that exceeds the cleaning schedule, and allows bypass FOG to reach the sewer during peak cooking periods. Oversizing wastes money and space but creates fewer operational problems.

If you are taking over an existing restaurant space, verify that the existing grease trap or interceptor is appropriately sized for your planned menu and cooking volume. A light-cooking predecessor’s trap may be inadequate for a high-volume kitchen producing significant FOG from fryers, grills, and saute stations. Add your anticipated flow calculations against the existing capacity before assuming the infrastructure is adequate.

Cleaning Frequency and the Trigger Rule

According to the EazyGrease guide, cleaning frequency depends on trap type and usage volume:

The specific trigger — 25 percent for interceptors — is not arbitrary. It is the threshold at which accumulated FOG begins to interfere with the trap’s hydraulic separation function, meaning FOG starts bypassing the separation layer and escaping through the outlet.

A kitchen that runs 500 covers per day with significant frying and grilling will fill an interceptor faster than a 100-cover operation with limited fried food. Build your cleaning schedule around your actual grease generation rate, not just the calendar minimum.

The Cleaning Process

Point-of-use traps under sinks are typically cleaned by kitchen staff. The process:

1. Remove and set aside the trap cover
2. Scoop out the accumulated FOG layer from the surface using a scraping tool
3. Remove the solid sludge from the bottom using a pump or scooping
4. Place removed material in a sealed, appropriate disposal container (not in general trash or down the drain)
5. Wipe down the interior surfaces with a dry cloth — never use hot water to melt grease during cleaning, as this pushes FOG into the drain
6. Reassemble the trap, verify seals, and confirm flow is restored
7. Record the cleaning in the maintenance log

In-ground interceptors require a licensed grease hauling company with appropriate vacuum equipment. Staff do not perform this cleaning themselves. The service company pumps the interceptor contents, disposes of them per local environmental regulations, inspects the outlet pipe and seals, and provides a service manifest that becomes part of your maintenance records.

Documentation and the Grease Control Log

According to the EazyGrease guide, maintenance records are a legal requirement in most jurisdictions. The Grease Control Log must include:

• Date of each cleaning or service
• Volume of material removed (gallons pumped for interceptors)
• Name of person or company performing the work (with license number for professional haulers)
• Confirmation that the trap was reassembled correctly and is functioning
• Signature of the responsible party

Local sewer authorities and health departments may request these records during inspections. A well-maintained log is evidence of responsible FOG management and a defense against allegations of non-compliance. A missing log is itself a violation in some jurisdictions, regardless of whether the trap is actually clean.

Keep records for a minimum of three years, or longer if your local authority requires it.

Prohibited Practices

According to the EazyGrease guide, specific practices are prohibited and subject to fines in most jurisdictions:

Chemical additives: Bleach, enzymes, emulsifiers, and commercial grease-dissolving products must never be added to grease traps. These products do not eliminate FOG — they dissolve or emulsify it in a way that allows it to pass through the trap and into the sewer system. Additionally, many of these chemicals kill the beneficial bacteria that naturally break down FOG within the trap, making the problem worse over time. Many jurisdictions impose fines when inspectors detect chemical additives in trap contents.

Hot water flushing: Running very hot water or steam to melt grease during cleaning pushes FOG through the outlet rather than removing it. The goal of cleaning is removal, not displacement.

Connecting garbage disposals: In many jurisdictions, commercial garbage disposals (food grinders) cannot discharge into a grease trap. The shredded food solids rapidly fill the trap’s sludge layer and dramatically shorten cleaning intervals. Some codes prohibit this connection entirely.

Discharging cooking oil directly: Spent fryer oil, grease skimmed from stocks, and similar high-concentration FOG should go into a designated used cooking oil collection container for commercial recycling — not down the drain. This not only keeps it out of the trap (where it would fill it immediately) but often has a recovery value through cooking oil recycling programs.

Automatic Grease Removal Units (AGRUs)

For high-volume operations that generate large quantities of FOG, automatic grease removal units represent a more sophisticated solution. According to the commercial kitchen plumbing guide, AGRUs continuously skim accumulated grease into external collection containers, reducing the labor demands of manual cleaning and maintaining consistent trap performance.

AGRUs typically require cleaning of their skimming mechanism and collection container on a weekly schedule, but they prevent the rapid buildup cycle that requires frequent full pump-outs for very high-volume operations. The upfront cost is higher than passive traps, but the ongoing maintenance cost can be lower when factoring in the frequency of professional pump-out services.

What Happens Without Compliance

The consequences of grease trap neglect follow a predictable escalation. A blocked building sewer lateral is an emergency plumbing call, typically costing $500 to $2,000 plus potential damage to the plumbing system and kitchen downtime. A sewer authority investigation following a reported overflow can result in fines ranging from hundreds to tens of thousands of dollars depending on the jurisdiction and severity. Repeated violations in some jurisdictions can result in forced suspension of operations until compliance is demonstrated.

Environmental consequences — FOG discharging into waterways — trigger separate regulatory frameworks with their own penalty structures.

None of this is hypothetical. Municipal sewer authorities actively monitor FOG discharge, particularly from restaurant districts, and trace violations back to the source through drain investigation.

The maintenance program is not expensive. Monthly cleaning of under-sink traps is a 30-minute task. Quarterly interceptor service runs $300 to $800 depending on size and location. The documentation takes five minutes to complete. Against the cost of non-compliance, this is a straightforward investment.

→ Read more: HVAC, Plumbing, and Fire Suppression: The Infrastructure That Keeps Your Kitchen Legal and Safe

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