FAQs - Grease Traps

If you have high levels of fats and grease you should use a grease trap. This would be fitted before discharging to the sewer.

Damage to sewer systems from FOGS can be extremely costly to local authorities and so there is much legislation surrounding best practices and correct disposal of fats, oils and grease, particularly for commercial food premises. If your property is connected to the mains drainage system and you’re serving hot food to the public or your staff, Building Regulations (document H, section 2.21) state you should have a grease trap or another effective means of grease removal fitted.

If you operate a commercial kitchen, such as a café, a pub, a takeaway service, a restaurant, a bakery or a staff canteen, a grease trap could help you to effectively manage your FOGS.  

It is estimated that nearly half a million tonnes of grease and fat enter the UK sewerage system each year, causing blockages and damage to pipes and wastewater equipment. Grease builds up inside pipes as it sticks to pipe walls and, if it enters a natural water course, fats, oils, grease and starch (FOGS) can seriously damage the environment. This damage is extremely costly to local authorities so proper management of FOGS is heavily enforced. Failure to effectively manage buildup could lead to heavy fines or even closure of commercial businesses.

Grease traps collect and reduce the number of FOGS entering the main sewers, helping to prevent drain blockages, bad smells and pest infestations. They can be located above or below ground, inside or outside your property, but positioned within the wastewater drain that connects your sinks and appliances to the sewer system. Fats and oils are much less dense than water, so they float to the top so, when wastewater enters a grease trap, it slows the water flow down significantly, separating solids to the bottom layer, wastewater in the middle and FOGS at the top. Wastewater is then allowed to flow into the sewer, while the FOGS are trapped.

Water and oil don’t mix. Animal fats and vegetable oils are much less dense than water, so they float to the top. In a grease trap, waste that flows through is slowed down and allowed a settlement period where solid waste sinks to the bottom and FOGS float to the top. A trap on the outlet prevents FOGS flowing through, permitting only the cleaner middle layer of wastewater to flow into the sewer system. Your grease trap needs to be properly maintained to ensure its continued effectiveness with regular cleaning required every two to four weeks by a licensed contractor.

Grease traps ensure grease and other build-up does not enter the main sewer system. Whether they’re attached to sinks, dishwashers or any other wastewater appliance that produce FOG, grease traps all perform the same basic function, with perhaps slightly different approaches. The size of the grease trap you’ll need will depend on the flow rate of the wastewater running through it — the higher the flow rate, the bigger the grease trap. At Tanks Direct we stock a wide range of grease traps in different size options to suit every flow rate.

Grease traps are a popular method of managing fats, oils and grease. At Tanks Direct we stock two types of grease traps for FOGS management — manual and automatic. Both do the same job of separating FOGS, solids and water within the tank, helping to prevent grease related issues. By slowing the flow of waste as it enters the grease trap and letting the wastewater cool, the elements naturally separate with solids sinking to the bottom, FOGS floating to the top and water remaining in the middle. What happens with each of these elements next is what differentiates a manual and automatic grease trap.

Manual grease traps are inexpensive and cheap to install. They simply contain and hold the FOGS until they are cleaned out. Automatic grease traps, also known as Automatic Grease Removal Units (or AGRUs), are more expensive than manual grease trap. However, automatic units systematically reheat and skim out the top layer of the tank where the FOGS sit, depositing it into a container where it can be disposed of easily. A separate filter catches any solid matter, which can be easily accessed and removed for disposal.