Scroll Top



Frequently Asked Questions

All commercial premises that are likely to produce fats, oils or grease (FOG) must have a pre-treatment device known as a grease trap, grease separator, or grease interceptor. This device must be sized, installed and maintained appropriately to prevent FOG from entering Council wastewater networks and/or the environment. FOG comes from the food residue that is on used plates and cookware in commercial kitchens and is the main cause of blocked pipes in wastewater networks.

Yes. A grease trap not only collects grease but also removes fats and oils from the wastewater. Fats and oils are generated from using cooking oil, salad oils for dressing, butter, margarine, shortening and mayonnaise. Grease is generated even while baking.

A grease trap works by slowing down the flow of warm/hot greasy water and allowing it to cool. As the water cools, the grease and oil separate and float to the top of the grease trap. The cooler water, with less grease, continues to flow down the pipe to the sewer. The grease is actually trapped by baffles, which cover the inlet and outlet of the tank, preventing grease from flowing out of the trap.

Grease traps are generally separated into three categories: external passive or hydromechanical, internal under bench grease removal, and internal under bench grease converter. For more information on these types of grease trap go to page Which Grease Trap.

Automatic grease traps can be installed internally and do not require enzymes to be added. For more information on how grease removal units work go to page Which Grease Trap. For more information on models available from MACTRAP go to page Grease Boss EasyClean.

A grease converter is suitable for internal use and removes fat, oil and grease (FOG) from waste water by automatically adding enzymes to bioremediate the waste. For more information on how grease converters work go to page Which Grease Trap. For more information on models available from MACTRAP go to page Grease Converter ChemiClean

In general, a grease trap and a grease interceptor are interchangeable terms used for any grease removal unit. But technically, a grease trap is small-sized equipment installed in the plumbing system inside a facility. Whereas, a grease interceptor is large-sized equipment installed outside the facility, usually under the ground.

In simple terms, we work out how long we need to settle the wastewater to separate the FOG, and that determines the size.  For more information on sizing a grease trap go to page  What Size Do I Need.

Risers are needed when a below ground grease trap is installed at a depth where the access points on the top (for servicing) are below ground level. Risers are attached to the top of the tank and have removable covers for cleaning that are suitable for either pedestrian or vehicular traffic. For more information go to page Grease Traps and see the section Covers and Risers.

Generally speaking, a grease trap (external or under bench) should receive a professional empty and clean every six months. However, this is affected by what you are allowing to enter the grease trap and how much fat, oil and grease is being removed and cleaning may be required every three months. For example, a kitchen producing high fat content fat food will need more frequent emptying than say, a salad bar. The amount of food scraps allowed to enter the grease trap will also affect how often it will need to be emptied.


Once food scraps enter a grease trap they cannot get out unless they are removed when the grease trap is being emptied. Food sediment builds up and causes blockages and rotting food causes bad smells. If you use a good sink filter then most food scraps can be captured before the wastewater enters the grease trap. For more information about managing your grease trap go to page User Maintenance. For more information specific to your type or model go to page User Manuals.

Grease traps back up either because they need to be cleaned or because of an outlet or drainage blockage. Buying a large unit would mean you wouldn’t need to clean it as often because there is more storage capacity of grease. But all grease traps will clog if you do not clean out the grease regularly. Every commercial kitchen should have a regular maintenance schedule for cleaning out their grease trap.

Grease should never be disposed of down the sink, as it will solidify while flowing through the pipes and cause blockages and backups. This can result in severe damage to the plumbing systems and problems with the city sewage systems which may result in penalties. Grease traps are only meant for collecting residual FOG from cooking.

Dishwashers, woks, rotisserie ovens, combi ovens, duck cookers and coffee makers may have wash processes that need to be taken into consideration. In addition, coffee grains, flour, and pasta can interfere with grease trap operation. We can design systems that will meet your individual trade waste requirements.

Support • Information • Design • Sizing

Need Help?