How to unblock a sink: plunger first, then the U-bend

2 min read · 7 steps · Updated 3 October 2026

Water that drains slowly or stands in the sink nearly always means a plug of grease and food in the kitchen, or hair and soap in the bathroom, sitting in the first metre of pipe. You can clear that yourself in a few minutes, with tools that cost very little.

If you rent, tell your landlord about problems with pipes or with appliances that belong to the flat before you try anything beyond these simple steps.

Step by step

1. Try the plunger

   Leave or add enough water to cover the rubber cup. Block the overflow hole with a wet cloth, and on a double sink the second plughole too. Press the plunger over the drain so it seals, pump hard up and down several times, then pull it away and see whether the water runs off. Repeat a few times.

   Done

2. Get ready to open the U-bend

   The U-bend, or trap, is the curved piece of pipe under the sink. Clear the cupboard, lay down an old towel and put a bucket or bowl directly below it. Water will gush out when you open it.

   Done

3. Unscrew the U-bend

   Undo the plastic nuts on both sides by hand, or with a spanner if they are tight. Tip the water and the sludge into the bucket.

   Done

4. Clean it

   Push out the debris with a bottle brush or an old toothbrush and wash the part in warm soapy water in another sink or in the bucket. Look into the open pipe ends as well and pull out what you can reach.

   Done

5. Put it back and test

   Check that the rubber washers sit in place, screw the nuts back on firmly by hand, and run the tap for a minute. Feel around the joints with a dry finger or tissue for drips.

   Done

6. In the bathroom: go after the hair

   Pour about half a litre of hot tap water down the drain, then use the plunger. A plastic hair snake, a thin strip with barbs, pulls out hair from the top without opening anything. A drain unblocker made for hair and soap is the next step.

   Done

7. Use chemical unblocker with care

   Follow the pack exactly, wear gloves, keep your face away and air the room. Never mix it with other cleaners or follow it with a different product, and do not use a plunger on a sink that has unblocker standing in it.

   Done

Good to know

Bicarbonate of soda with vinegar fizzes nicely but did not clear real blockages in tests by the UK consumer magazine Which?. It may help with a smell.

To prevent the next blockage: scrape plates into the bin, wipe grease from pans with kitchen paper, never pour oil or fat down the drain, keep coffee grounds out, and use a strainer over the plughole.

If the sink is still blocked after you have cleaned the U-bend, or several drains in the home are slow at once, the blockage is further down. Call a drainage specialist, or your landlord if you rent.

Use one plunger for sinks and a different one for the toilet.

In short: Plunger with water in the sink and the overflow blocked. Then bucket under the U-bend, unscrew, clean, refit, test for leaks. Hair snake in the bathroom. Chemicals last and with care.