FOG tips this Festive Season

Fat, oil and grease (FOG) in wastewater discharges, along with wet wipes, are a major cause of blockages in sewers and failures at sewage pumping stations. Approximately 300,000 blockages occur in the UK annually, costing the water industry over £100 million to clear. For the water companies’ customers, this can mean a toilet out of action, flooding of gardens and even internal flooding of properties. Nobody wants sewage backing up in or near their property at any time of the year, but the festive season is possibly the worst-case scenario. The thought of a Christmas tree surrounded by presents floating in the 3Ps (pee, poo and paper) doesn’t bear thinking about, but it could happen without care and consideration for home sewers.


The complete elimination of FOG is neither practical nor absolutely necessary. A small amount in wastewater discharges, for example from domestic properties that are aware of the correct disposal of FOG, is unlikely to cause a serious problem. Similarly, washwater discharges from food service establishments (FSEs) shouldn’t cause any difficulties if the FSEs carry out good kitchen practice, which includes the use of equipment with FOG traps and separators. However, a lack of good practice can result in significant volumes of FOG being discharged into sewers, and this time of year is a particular challenge.

At home with(out) FOG

All across the land, we will be sitting down to meals during the month of December that probably have a higher fat content than usual, whether at home or eating out. The startling fact that the fat from just one cooked turkey is enough to fill a pudding bowl, never mind the gravy and cooking fat from all the roasted potatoes, is sobering. If that fat is poured down a sink it could easily block the pipes closest to a home, which are often only 100mm in diameter. Once the FOG enters a drain and cools, it solidifies and then blocks the flow of everything else that’s being poured down a sink or flushed from a toilet, potentially sending it all back inside or surging out of manholes if the blockage is further along the sewerage system.

To help reduce (or even eliminate) our personal, family and friends’ contribution to the FOG problem, here are three easy-to-remember tips:

  • Pour all liquid fats, oils and grease into a heat-resistant container and leave to cool, then scrape the solidified grease into the general waste bin.
  • Wipe all dinner plates, serving bowls and utensils with kitchen paper before washing up or loading them into a dishwasher then dispose of the paper in the general waste bin.
  • Only allow the 3Ps down the loo: pee, poo and paper. (Be sure to have a bin and bags for visitors to put their non-flushable items in. You could even provide a FabLittleBag and encourage your female visitors to #beabinnernotaflusher).

FOG removed from a sewer

Out and about with FOG

On the commercial front in the UK, the law does not currently require FSEs to install FOG separators, unless they are new properties or there is a change of use. In addition, the water industry does not have any power to enforce FOG management other than retrospective action. They have to rely mainly on Environmental Health Officers whose main concern is food hygiene and they often do not have knowledge and time to advise on the best possible solution for a FOG management system.

However, it is a criminal offence to discharge any matter that is likely to injure sewers or drains or could affect treatment and disposal. Thus, in theory, a FSE that discharges FOG in the wastewater that leads to a blockage is guilty of an offence. However, the onus is on the water and sewerage company (WaSC) to prove “beyond all reasonable doubt” that the named FSE was responsible. Where there is an isolated FSE this may be relatively easy to prove. Conversely, where there is a cluster of FSEs (and that is where the majority of the problems are found), proving who is responsible can be far more difficult.

The main approach by the water industry for dealing with festive FOG at FSEs is, again, by increasing awareness of the problem and promoting good practice in commercial kitchens, particularly when Christmas parties are at full tilt and many FSEs are operating at maximum capacity.

Created by potrace 1.16, written by Peter Selinger 2001-2019

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Created by potrace 1.16, written by Peter Selinger 2001-2019

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Gosia Druzkowska

Project Manager

Gosia is an accredited Chartered Water and Environment Manager and has a MEng in Environmental Engineering: Water Supply, Wastewater Treatment and Solid Waste Disposal. She joined WRc in April 2008 and is responsible for delivering projects to time, budget and to a high standard of quality. Recent projects she has managed include a number of collaborative research projects on invert corrosion, efficient pumping, CCTV and manhole rehabilitation and a single client research project on blockage formation and impact of rainfall. Gosia managed United Utilities project on experiment design and assessment for wipes disposal campaigns, and FOG issues review for Severn Trent Water.

2023-12-19 09:06:00