Dealing with fat, oil and grease in your food business

You can fit grease traps to kitchen drainage systems to prevent build-up of grease and fat in drains and sewers. The grease traps are designed to separate out the fats, oils and grease - which remain in the trap - and allow the clarified wastewater to flow out to the sewerage system.

Design of grease traps

The grease trap unit should be the correct size to handle the amount of wastewater from your premises. You should empty out the collected fats, oils and grease regularly and dispose of them correctly. You should keep a written record of maintenance - see how to dispose of fat, oil and grease in your food business.

Use of grease traps

There are three key factors to consider to make sure your grease trap works correctly:

• Temperature - the water discharged from a dishwasher is usually 50-80 degrees Celsius and the average pot wash water temperature is around 40-50 degrees Celsius. At these temperatures, fats and grease stay in solution and may pass straight through the grease trap. 
• Time - you must allow enough time in the grease trap for the grease to cool and separate from kitchen wastewater.  
• Volume - for any grease trap to collect grease efficiently, it needs enough volume to handle the amount of wastewater leaving the business premises. Smaller volumes may pass through the grease trap. 

Maintenance of grease traps

You must maintain your grease trap to ensure it keeps working correctly. A neglected trap will quickly fill with grease. Filled traps can overflow to the drainage system, causing hygiene and health problems. You should keep a written record of maintenance for the grease trap.

You may find it more convenient to buy in services on contract to empty your traps regularly and properly dispose of the contents.

Cost of grease traps

The cost of a grease trap depends on size and fit, and can range from £400 to £500 for a small trap to between £3,000 and £5,000 for a large underground trap.

Running costs will also vary - you will need to maintain an under-sink unit daily, whereas you only need to maintain an underground external unit fortnightly or monthly.

Portable grease traps are available and cost around £700 per year.