How to Unblock a Sink (Without Wrecking Your Pipes)

A slow or blocked sink is one of the most common plumbing problems there is, and most of the time you can clear it yourself. Work through these in order, from least to most effort.

1. Hot water (not boiling)

For a kitchen sink slowed by grease, pour a kettle of very hot — but not boiling — water down slowly. Boiling water can soften the joints in plastic waste pipes. Hot water and washing-up liquid will shift a surprising amount of fat.

2. Plunger

1. Leave a few centimetres of water in the sink so the plunger seals.
2. Block the overflow with a damp cloth — otherwise you're just pushing air out of the overflow hole. On a double sink, block the other plughole too.
3. Plunge firmly up and down 15–20 times, then pull away sharply.

3. Clean the trap

The U-shaped (or bottle-shaped) trap under the sink catches most blockages. Put a bucket underneath, unscrew it by hand, and empty it out. You'll often find the culprit straight away — hair in a bathroom basin, food and fat in a kitchen sink. Rinse it, refit it hand-tight, and run the tap to check for drips.

4. Drain snake

If the trap's clear, the blockage is further along the waste pipe. A cheap plastic drain snake or a hand auger can reach it. Feed it in, twist, and pull back slowly.

What about chemical drain cleaner?

Use it sparingly, and never if there's standing water in the sink or you've already used a plunger — the splashback is caustic. Never mix different products. Bicarbonate of soda and vinegar is gentler, but works better as regular maintenance than on a proper blockage.

Stop it happening again

• Don't pour fat or oil down the sink — wipe pans with kitchen roll first.
• Use a strainer to catch food scraps and coffee grounds.
• Pull hair out of basin plugholes regularly.
• Run hot water and washing-up liquid down the kitchen sink every week or so.

When to call a plumber

• More than one sink, bath or toilet is draining slowly — that suggests a blockage further down the system.
• You can smell drains, or water is coming back up somewhere else.
• The waste pipe is leaking or damaged.

If you're in Preston or nearby, we're happy to help — see our plumber cost guide for typical prices, then call 07949 075721 or use the form below.