Commercial Grease Interceptors in Quebec: Operation, Maintenance, and Regulations

November 6th, 2026

Commercial kitchens discharge wastewater that often contains fats, oils, grease, and food particles. Without the right equipment, these materials can cool, harden, and accumulate inside drain lines. The result may be slow drainage, unpleasant odors, sewer backups, emergency service, or a temporary interruption to kitchen operations.

A commercial grease interceptor, commonly called a grease trap, captures some of this material before it reaches the drainage system. Its performance depends on proper sizing, code-compliant installation, good kitchen practices, and maintenance performed before the unit loses too much of its working capacity.

This guide explains how commercial grease interceptors work, how to determine an appropriate cleaning schedule, and which requirements Quebec businesses should verify. Municipal sewer rules can differ, so the installation and maintenance plan should be confirmed with the applicable authorities and qualified professionals.

Key Takeaways

• A commercial grease interceptor must be selected for the actual flow rate, connected fixtures, kitchen activity, and applicable requirements. An undersized or incorrectly connected unit may allow excessive grease to enter downstream piping.
• The 25% rule is a widely used maintenance trigger, not a universal legal schedule. The proper cleaning frequency depends on measured accumulation, manufacturer instructions, and requirements imposed by the municipality or sewer authority.

What Is a Commercial Grease Interceptor?

A grease interceptor is installed on part of a commercial kitchen’s drainage system. It slows wastewater long enough for materials to separate by gravity. Fats and oils, which are generally lighter than water, rise toward the surface. Heavier food particles settle at the bottom, while water moves through the middle of the unit and continues toward the sewer.

Baffles or internal compartments improve separation. The process is not perfect, however. If wastewater enters too quickly, arrives at a very high temperature, exceeds the unit’s rated flow, or passes through an interceptor that is already too full, more grease can escape into downstream piping.

Hydromechanical vs. Gravity Grease Interceptors

The appropriate unit depends on the kitchen design and the volume of wastewater that must be treated. The following table summarizes the two most common categories.

Type of unit	Common installation	Typical maintenance	Main factor to verify
Hydromechanical grease interceptor	Near one or more fixtures, under a counter, or in an accessible mechanical area	Relatively frequent inspection and cleaning based on accumulation	Rated flow, grease storage capacity, accessibility, and connected fixtures
Gravity grease interceptor	Larger tank, often installed outdoors or underground	Pump-out by a provider equipped to remove and transport grease waste	Working volume, pump-truck access, venting, location, and local requirements

Some facilities use automatic grease-removal devices. Regardless of the technology, the unit must suit real operating conditions. The amount of space available under a sink is not enough information to select the correct model.

Which Fixtures Should Connect to a Grease Interceptor?

The connection plan must follow Quebec’s Construction Code, the applicable standard, manufacturer instructions, and requirements set by the authority having jurisdiction. Food preparation sinks, pot sinks, and other fixtures may be included when their wastewater contains fats, oils, or grease.

Do not assume that every kitchen fixture should be connected in the same way. A toilet must not discharge through a grease interceptor. Dishwasher connections also require careful review because high water temperatures and some detergents can reduce separation performance. A qualified contractor should confirm the proposed arrangement before the drainage system is installed or modified.

Are Commercial Grease Interceptors Required in Quebec?

Chapter III, Plumbing, of Quebec’s Construction Code requires interceptors where fats, oils, or grease may impair the drainage system. Grease interceptors must comply with the CSA B481 Series and be selected and installed in accordance with CSA B481.3. Quebec’s building authority explains these requirements in its booklet on changes to the Plumbing chapter.

Sewer-use rules create a separate layer of obligations. A municipality or regional authority may regulate discharges, cleaning practices, maintenance records, inspections, sampling, and grease-waste disposal. Businesses must therefore check the rules that apply to their specific address instead of relying on practices used in another municipality.

Restaurants, cafeterias, institutional kitchens, food-preparation counters, and other commercial operations may be affected even when they do little frying. The nature of the wastewater and the plumbing configuration determine the requirement, not the business label alone.

How Is a Commercial Grease Interceptor Sized?

Sizing should not be based only on seating capacity or the amount of room beneath a sink. Important factors include the flow rate and capacity of connected fixtures, simultaneous use, wastewater temperature, and the amount of grease produced.

An undersized unit may move wastewater through too quickly for effective separation. An oversized or poorly located unit can also create accessibility, maintenance, or performance problems. Selection must be based on the project’s operating data and the sizing method required by the applicable standard.

Before purchasing a unit, have its model, location, connections, venting, and cleaning access confirmed. The commercial plumbing services offered by Plomberie Richard et Fils can help assess the building’s plumbing needs and drainage layout.

How Often Should a Commercial Grease Trap Be Cleaned?

There is no single cleaning interval that works for every business. A small interceptor serving a busy kitchen may require frequent service, while a large gravity unit operating under different conditions will follow another schedule.

The 25% rule is commonly used as a practical trigger. It calls for cleaning or pumping the unit when the combined thickness of the floating grease layer and settled solids reaches about one-quarter of the usable liquid depth. Beyond this point, the separation zone becomes smaller and more material can be carried toward the outlet.

This guideline does not replace manufacturer instructions or local requirements. After a new unit is commissioned, frequent initial checks and measured accumulation can help establish a maintenance schedule that reflects the kitchen’s actual operation.

How Do You Measure Grease and Solids?

The inspection method depends on the equipment. For an accessible hydromechanical unit, a trained person may open the cover using appropriate safety precautions and measure the accumulated layers with a tool intended for that purpose. The cover must then be properly reinstalled to maintain a seal and limit odors.

Large tanks require additional caution. They may present hazards related to gases, open access points, and confined spaces. No one should enter a grease interceptor tank. Inspection and pump-out should be assigned to a provider with suitable equipment, training, and authorization.

Each service visit should be documented. A maintenance record may include the date, measured levels, volume removed, condition of baffles and seals, observed defects, and service provider’s name. These records help refine the cleaning schedule and may be required by the local authority.

What Are the Signs That a Grease Interceptor Needs Service?

Slow drainage at several kitchen fixtures may indicate reduced flow through the interceptor or a restriction in downstream piping. Recurring backups, visible grease accumulation, an abnormally high liquid level, or grease observed near the outlet also warrant inspection.

Odors should be diagnosed instead of automatically blamed on the grease trap. They may result from accumulated organic matter, an improperly sealed cover, a dry trap, a venting problem, or a leak. Plomberie Richard et Fils has drain-cleaning, hydro-jetting, and camera-inspection equipment that can help identify the cause of persistent drainage problems.

How Should a Commercial Grease Trap Be Cleaned?

Proper cleaning removes the floating grease layer, settled solids, and residue attached to walls or baffles. Skimming only the visible grease from the surface does not restore the unit’s full working capacity. Internal components, gaskets, the cover, and accessible connections should also be inspected.

Trained staff may be able to clean some small interceptors when the manufacturer’s instructions, workplace-safety measures, local rules, and disposal requirements allow it. Large gravity units are generally pumped by a specialized provider equipped to remove, transport, and dispose of the waste appropriately.

Grease waste must not be returned to a sink, floor drain, or toilet. Chemical, enzyme, or bacterial products intended to liquefy grease should not replace physical cleaning. They can simply move the problem into downstream piping or the sewer and may be prohibited or discouraged by the local authority.

How Can a Kitchen Reduce Grease Buildup?

Grease control starts before dishwashing. Plates, pans, and utensils should be scraped or dry-wiped before washing. Suitable sink strainers can capture food particles. Used cooking oil should be collected in a dedicated container and sent through an appropriate recovery service.

Avoid pouring boiling water into drains in an attempt to clear grease. Heat may move the material farther into the drainage system, where it can cool and harden. Staff training, a simple written procedure, and one person responsible for maintenance records are often more effective than responding after a backup occurs.

What Does Professional Grease Interceptor Service Include?

Depending on the equipment and service agreement, a visit may include measuring grease and solids, pumping the full contents, cleaning walls and baffles, inspecting accessible components, checking the cover, and providing a service record. A flow problem may also require inspection or cleaning of upstream and downstream piping.

Pump-out and plumbing work are not always performed by the same provider. A specialized waste company may remove and transport the contents, while a plumbing contractor addresses the installation, fixture connections, or drain lines. Ask who is responsible for each part of the work and which records will be provided.

Have Your Commercial Plumbing Inspected

A commercial grease interceptor protects drain lines only when it is properly selected, connected, and maintained. If your kitchen has slow drains, persistent odors, or recurring backups, the entire drainage system should be assessed instead of pumping the interceptor without investigating the cause.

Plomberie Richard et Fils serves Montreal’s West Island and surrounding communities for commercial plumbing, drain cleaning, and inspection needs. To discuss your installation or request an assessment, contact the Plomberie Richard et Fils team.

Frequently Asked Questions About Commercial Grease Traps

What is the difference between a grease trap and a grease interceptor?

The terms are often used interchangeably. In technical usage, a grease trap commonly refers to a compact hydromechanical unit installed near fixtures, while a grease interceptor may describe a larger gravity tank. Quebec regulatory documents generally use the French term séparateur de graisses.

Is the 25% rule mandatory in Quebec?

It is a widely used maintenance guideline, not a universal schedule for every establishment. Manufacturer instructions, measured accumulation, and municipal requirements must also be followed.

How often should a commercial grease interceptor be pumped?

The appropriate interval depends on grease and solids production, unit capacity, and local rules. Begin with frequent inspections, record the measured levels, and establish a schedule that provides service before too much working capacity is lost.

Can employees clean a small under-sink grease trap?

Sometimes, provided the unit is designed for that type of maintenance and employees are properly trained. The manufacturer’s instructions, protective-equipment requirements, workplace procedures, and local waste-disposal rules must all be followed.

What should I do if the drains remain slow after pump-out?

Upstream or downstream piping may be partially blocked, or the installation may have a venting, slope, or connection issue. A professional inspection can determine whether drain cleaning, hydro-jetting, camera inspection, or a plumbing correction is required.