Environmental impact

Fat, oil and grease cause major problems to drains and sewers. When they are disposed of down kitchen sinks or drains they cause blockages; when they enter rainwater pipes or gullies they cause pollution in streams and rivers.

History of the problem

The eating habits of the nation are changing, people are eating out much more frequently than they did in the past and the number of food outlets is increasing. Fat, oil and grease in liquid form may not appear to be harmful, but as it cools it congeals and hardens. It sticks to the inner lining of drainage pipes and restricts the wastewater flow causing the pipes to block. Using detergents or bleach may appear to help but this is only temporary as the mixture soon turns back to thick or solid fat. These fat blockages can result in sewer flooding, odour problems and the risk of rat infestations, both near and beyond your premises.
In fact, every outlet disposing of fat, oil and grease into sinks and drains is at risk of experiencing damaging and costly drainage problems but there are ways that you can help.


Training for all food handlers should include instruction on why it is important to keep fats, oils, grease and food waste out of drains and sewers. It should be explained to each food handler that failure to do this can lead to expensive costs for the business to unblock drains and clean up the area. Bad practice can result in a public health nuisance, prosecution and unwanted negative publicity as well as disruption to normal business.

Preparation prior to washing

Plates, pots, trays and utensils should be scraped and dry wiped with a disposable kitchen towel prior to putting them in the sink or dishwasher and the scrapings placed in the bin. All sinks should have a strainer for placing in the plug hole to prevent waste food from going down the drain. Waste food collected in the strainer should be placed in the rubbish bin ready for collection.

Grease traps/grease interceptors

Grease traps are specially designed units which are placed in drain pipes to separate the fat, oil and grease from the rest of the wastewater. The wastewater then continues to flow to the sewage works for treatment while the grease is retained in the trap to be collected by a licensed waste oil collector at regular intervals. These units can be highly effective if they are correctly installed, serviced and maintained. A written record of maintenance must be kept. Proper location and size of the unit to suit the operation on the premises is important to ensure it is efficient at preventing the grease causing problems in the drains.

Enzyme dosing systems

Special enzymes are used to break down fats, oils and greases in the drainage system. They are supplied by specialist companies and can be used with grease traps. Enzymes can be effective where properly used, but keeping fat, oil and grease out of drains in the first place should make them unnecessary.

Waste oil storage

Waste oil comes from sources such as deep fat fryers, woks, frying pans and baking trays. Waste oil at food establishments should be collected in an air-tight container to prevent odours and rats. The container should be stored in a secure area, clear of all drains, to prevent spills and leakages.


The disposal of use oil should be closely managed by ensuring waste oil collectors are licensed and the waste is being taken to an appropriate disposal site/ licensed waste management site.

Excerpt from https://www.nwl.co.uk/_assets/documents/FOG_A4_12_page.pdf


Michael Myles

JAPHI Executive Member