Fat, Oil and Grease: The UK’s Growing Drain Crisis

Britain's sewers are under siege. Every year, water companies across England and Wales deal with over 300,000 sewer blockages, and the majority are caused by a single culprit: fat, oil and grease — known in the industry as FOG.

The problem costs the water industry an estimated £100 million a year to fix, and individual homeowners face bills of hundreds of pounds for emergency drain clearance. In the worst cases, sewer blockages cause raw sewage to back up into homes or overflow into rivers and waterways.

How FOG causes blockages

When cooking fat, oil, or grease is poured down the kitchen sink, it's liquid and seems harmless. But as it travels through the drainpipe and cools, it solidifies. Over time, layers of solidified fat build up on pipe walls, narrowing the pipe until water can no longer flow freely.

In public sewers, FOG combines with other items that shouldn't be flushed — particularly wet wipes — to form massive "fatbergs." The most famous example was the Whitechapel fatberg discovered under London in 2017, which weighed 130 tonnes and stretched 250 metres — longer than Tower Bridge. A section of it is now preserved in the Museum of London.

The scale of the problem

According to Water UK:

• Around 366,000 sewer blockages occur in England and Wales every year
• Approximately 75% are caused by FOG and non-flushable items
• Clearing blockages costs the industry £100 million annually
• Sewer flooding affects thousands of homes each year
• Blockages contribute to sewage overflows into rivers — a growing environmental concern

The problem has been compounded by the growth of food delivery services. With more people cooking at home and ordering fatty takeaways, the volume of FOG entering the drainage system has increased significantly since 2020.

What water companies are doing

Most water companies now run public awareness campaigns. Thames Water's "Bin It" campaign encourages residents to scrape plates into the bin and pour cooking oil into a container for disposal. Southern Water, Anglian Water, and others run similar programmes.

Some councils now provide free "fat traps" — small strainers that sit in the plughole and catch grease before it enters the drain. These are available from most local authority recycling centres.

What you can do

• Let fat cool and bin it. Pour cooking oil into an old tin or jar, let it solidify, and put it in the bin.
• Scrape plates before washing. Use kitchen roll to wipe greasy pans and plates before they go in the sink.
• Use a sink strainer. A cheap metal strainer catches food debris before it goes down the drain.
• Run hot water after washing up. This helps clear any residual grease from the pipes.
• Never pour oil down the drain. Even small amounts accumulate over time.

Already blocked?

If your kitchen drain is running slowly or you're experiencing bad smells, it's likely a FOG build-up is forming. Acting early prevents a full blockage. A professional drain clearance with high-pressure jetting will blast through the grease and restore full flow. Costs typically range from £100 to £250.