Kitchen Drain Blocked with Fat or Grease
Do not use chemical drain unblockers in combination with a plunger — the splashing of caustic chemicals is dangerous. Use one method at a time.
Fat and grease blockages are the most common cause of kitchen drain problems in the UK. When hot fat is poured down a drain it solidifies as it cools, progressively narrowing the pipe over months. Unlike hair blockages, fat requires either mechanical removal or a hot water/chemical treatment.
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Try boiling water first — carefully pour a full kettle of just-boiled water directly into the drain. For mild grease blockages this is often enough to remelt the fat and flush it through. Repeat 2–3 times.
Follow with a degreasing treatment — pour 125ml of washing up liquid into the drain, then a second kettle of boiling water. The detergent emulsifies the fat and flushes it away.
For stubborn blockages, use a biological or caustic drain cleaner (e.g. Buster Kitchen Plughole Gel, Mr Muscle, or HG). Follow the product instructions exactly. Do not mix products.
If chemical treatment doesn't clear it, use a plunger on the kitchen sink. Fill the sink with enough water to cover the plunger cup, block the overflow with a cloth, and plunge vigorously 15–20 times.
Remove and clean the bottle trap under the sink — unscrew the base of the U-bend into a bucket. Fat deposits here are very common and can be the entire source of the problem. Clean the trap in hot water and refit.
For blockages further in the waste run, use a drain rod or flexible hand drain auger (available from Screwfix, £15–25) — feed it into the 40mm waste pipe and work it through the blockage.
To prevent recurrence: never pour fat down the drain. Let it cool in the pan, pour into an old tin, and bin it. Monthly treatments with boiling water and washing up liquid will keep the drain clear.
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