How Often Should You Clean Your Grease Trap? (And What Happens If You Don't)

A commercial grease trap should be cleaned before grease and settled solids take up 25% of its working volume—and sooner if local rules require it. In Halifax, the current requirement for food-service establishments is monthly cleaning or cleaning when the combined grease and solids layer reaches 25%, whichever comes first.

That is the short answer. The more useful answer is that your kitchen may need service more often.

A small café and a busy full-service restaurant do not put the same load on an interceptor. Menu, meal volume, operating hours, equipment and the size of the unit all matter. The best schedule is based on actual measurements, not guesswork or what another restaurant happens to be doing.

How often should a restaurant clean its grease trap?

Use three checks:

Measure the buildup. Service the unit before grease and solids reach 25% of its working volume.
Check the local rule. Your wastewater authority may set a maximum interval even if the unit has not reached 25%.
Watch how your kitchen operates. A fry-heavy menu, longer hours or a seasonal rush can fill an interceptor faster than expected.

Halifax Water’s current guidance, for example, requires grease interceptors to be cleaned monthly or at the 25% point, whichever comes first. It also requires food-service establishments to keep two years of maintenance records and submit service records within seven days of cleaning.

Outside Halifax, the details may be different. Restaurants elsewhere in Nova Scotia, New Brunswick, Prince Edward Island, and Newfoundland and Labrador should check the sewer-use rules and permit conditions that apply to their location.

What does the 25% rule mean?

A grease interceptor separates kitchen wastewater into layers. Grease floats to the top. Heavier food particles and solids settle at the bottom. Water moves through the space between them.

As those layers grow, there is less room for the interceptor to do its job. The 25% rule identifies the point at which the combined grease and solids have taken up too much of the unit’s working capacity.

The calculation is straightforward:

(Grease depth + solids depth) ÷ total liquid depth × 100

Suppose the floating grease is 10 centimetres deep, the settled solids measure 8 centimetres and the total liquid depth is 80 centimetres:

(10 + 8) ÷ 80 × 100 = 22.5%

That interceptor is getting close. Waiting until the next routine visit could push it past the service point.

The Halifax Water Pretreatment Requirements Manual gives a useful example: if a restaurant reaches the threshold in two weeks, then two weeks—not one month—is the appropriate schedule for that operation.

A practical way to set your cleaning schedule

When there is no reliable service history, start by checking the interceptor weekly. Record the grease layer, solids layer and total liquid depth each time. After several checks—including at least one busy period—you will have a much better picture of how quickly the unit fills.

Then schedule service with a margin of safety. If the interceptor typically reaches 25% after three weeks, do not book cleaning for the last possible day. An unexpectedly busy weekend or a delayed appointment could put the unit over the limit.

Review the schedule whenever the kitchen changes. Adding fryers, expanding the menu, taking on catering work or extending hours can all increase the load.

Kitchen conditionWhat to doNo reliable service historyInspect weekly until a clear pattern developsGrease and solids are approaching 25%Arrange service and shorten the next intervalBuildup reaches 25% before the scheduled dateClean sooner and adopt the shorter scheduleBusiness volume or menu changesRecheck buildup instead of relying on the old scheduleLocal rules require more frequent serviceFollow the local requirement

Why do some grease traps fill faster than others?

The pace of buildup depends on what goes down the drain and how much wastewater moves through the kitchen. Common factors include:

Daily meal volume
Fried foods, meat, sauces, dairy and baked goods
The size and capacity of the interceptor
The sinks, drains and equipment connected to it
How well plates, pans and utensils are scraped before washing
Food solids entering the drainage system
Seasonal peaks, events and catering production
An undersized, damaged or poorly installed unit

This is why a standard calendar interval is only a starting point. Two restaurants with the same number of seats can produce very different amounts of fats, oils and grease.

What happens when a grease trap is not cleaned?

The first signs are not always dramatic. A sink may drain more slowly. Staff may notice an odour near the unit. Then the problem becomes harder—and more expensive—to ignore.

Drains can slow down or back up

An overloaded interceptor can allow grease and solids into downstream piping. There, the material can collect and contribute to blockages. The result may be slow drains, unusable sinks or a wastewater backup into the facility. Halifax Water specifically identifies pipe blockages and wastewater backups as consequences of poor interceptor maintenance.

Odours and pests can become a problem

Food material held inside an interceptor breaks down over time. If cleaning is overdue, seals are poor or components are damaged, persistent sour or rancid smells may follow. Those conditions can also attract flies and other pests.

An odour does not tell you exactly how full the trap is, but it is a good reason to inspect it promptly.

Kitchen operations can be disrupted

A blocked line can take a sink, dishwashing station or entire prep area out of use. Emergency pumping, drain clearing, sanitation and lost operating time tend to cost far more than planned maintenance.

The interceptor can deteriorate

Cleaning visits are also a chance to check baffles, walls, seals and fittings. Missing baffles, corrosion or other damage can reduce performance even when the unit has recently been emptied. Halifax Water notes that regular servicing can help extend the interceptor’s life and reduce odours.

The business can fall out of compliance

An overdue interceptor, missing records or prohibited maintenance practices can create problems during an inspection. Depending on the local authority, the business may have to clean, repair or replace the unit and address any related blockage or discharge.

The impact can extend beyond the restaurant

Grease that escapes into the sewer can accumulate in public infrastructure and contribute to blockages and overflows. At that point, the issue is no longer contained within one kitchen. It may affect neighbouring properties, wastewater operations and the environment.

Signs your grease trap may be overdue

Do not wait for a warning sign if the required service date arrives first. But if any of the following appear, check the unit promptly:

Connected sinks or floor drains are slow
Grease appears downstream of the interceptor
Sour or rancid odours persist
Drains gurgle or behave unusually
Grease and solids are close to or above 25%
Connected plumbing clogs repeatedly
Internal parts are corroded, damaged or missing
The maintenance log is incomplete or the service date has passed

What should happen during a proper cleaning?

A quick skim of the top layer is not a complete service. The job should include removing the floating grease, wastewater and settled solids; cleaning and inspecting the accessible internal components; and recording what was found.

At minimum, the service record should capture:

Date of service
Grease, solids and liquid-depth measurements
Condition of baffles, walls, seals and fittings
Work completed
Person or company that performed the service
Disposal information required by the local authority

Larger interceptors and units with difficult or hazardous access should be handled by a qualified service provider. Always follow the manufacturer’s instructions and local disposal requirements.

Can hot water, enzymes or chemicals clean a grease trap?

They do not replace physical cleaning. A product or process that moves grease through the interceptor may simply send the problem farther down the pipe.

Local rules vary, but Halifax Water specifically prohibits using enzymes, solvents, hot water or other agents as a grease-interceptor maintenance method. The contents still need to be removed and disposed of properly.

How can a kitchen reduce grease going down the drain?

Good habits will not eliminate servicing, but they can slow buildup and reduce avoidable problems:

Scrape plates, trays, cookware and utensils before washing.
Collect used fryer oil in a designated container—never a sink or floor drain.
Use strainers or screens to keep food solids out of the plumbing.
Wipe up grease and spills before mopping where practical.
Train every shift on the same fats, oils and grease procedures.
Keep the interceptor accessible for inspection and service.
Record inspections instead of relying on memory.

A grease trap is not the same as a kitchen exhaust system

These two maintenance jobs are sometimes confused, but they protect different systems.

A grease trap or interceptor captures fats, oils, grease and solids in kitchen wastewater. A commercial exhaust hood, filters and ductwork manage airborne grease created during cooking. Cleaning one does not satisfy the maintenance requirements for the other.

Commercial kitchens need separate inspection and cleaning schedules for both systems.

Frequently asked questions

Is monthly grease-trap cleaning enough?

It may be, but only if the interceptor stays below the 25% threshold and monthly service meets the local requirement. A busy kitchen may need cleaning every two weeks or more often. Measure the buildup to find out.

How can I tell when a grease trap is 25% full?

Measure the floating grease and settled solids. Add those depths, divide by the unit’s total liquid depth and multiply by 100. A service provider can take and document the measurements if your team is not trained to do so.

Does a grease trap need cleaning if it does not smell?

Yes. Smell is not a dependable measure of capacity. Follow the measured buildup, the local service requirement and the manufacturer’s instructions.

Can restaurant employees clean a grease trap?

It depends on the unit, access, staff training and local rules. Some small indoor units may be serviced in-house where permitted. Large outdoor interceptors generally require pumping equipment and a qualified provider. In either case, the entire contents must be handled and disposed of correctly, and the work should be documented.

Is a grease trap the same as a grease interceptor?

The terms are often used interchangeably. Technically, “grease interceptor” is the broader term. Smaller indoor units are commonly hydromechanical interceptors, while larger outdoor tanks are commonly gravity interceptors. The distinction matters because sizing, access and maintenance requirements can differ.

The bottom line

Do not choose a grease-trap schedule by habit. Check the unit, measure how quickly grease and solids accumulate, and clean it before they reach 25% of its working volume—or sooner when local rules say so.

It is a small piece of preventive maintenance compared with a blocked drain, wastewater backup or kitchen shutdown.

Need a more consistent commercial kitchen cleaning routine? Crystal Clean Maintenance provides commercial cleaning across Atlantic Canada. Talk to our team about a cleaning plan built around your facility, operating hours and standards.