How to unblock a sink: plunger, U-bend and drain snake, step by step

Why sinks get blocked

In the kitchen, fat, oil and grease set as they cool and trap food scraps, coffee grounds and rice. In the bathroom basin, hair binds with soap. Most blockages sit in the U-bend, the first bend in the pipe just below the plughole.

Method 1: use a plunger

1. 01

   Seal the overflow

   Cover it with a damp cloth or tape. On a double sink, block the other plughole too, or the pressure escapes there.

2. 02

   Add some water

   Enough to cover the plunger cup, so it seals over the plughole.

3. 03

   Place the plunger

   Centre the cup over the plughole and press until you feel it grip.

4. 04

   Pump firmly

   Push and pull up and down several times, a little harder each time, then lift it off.

5. 05

   Check

   When the blockage clears, the water drains away. Run the tap for a minute to flush the pipe.

A plunger works on blockages that can break up. If something solid has fallen in, such as a toy or a large piece of soap, plunging can wedge it further: open the U-bend instead.

Method 2: a burst of hot water

Fill a plastic drinks bottle with hot, not boiling, water, turn it upside down over the plughole and squeeze hard. The fast flow can push a soft blockage through. Keep boiling water away from plastic pipes and joints, as high heat can soften them. Extra-hot soapy water is no cure for fat in the pipes.

Method 3: clean the U-bend

This is the most effective method for most kitchen and bathroom sinks.

1. 01

   Prepare

   Empty the cupboard under the sink, put a bucket under the U-bend and have gloves and a towel to hand. If the sink is full, bail the water into a bucket first.

2. 02

   Unscrew the fittings

   Most plastic traps have a nut at each end that you can undo by hand. As they loosen, trapped water drains out, so go slowly.

3. 03

   Clean it

   Empty the trap, scrape out the debris with a bottle brush, an old toothbrush or a straightened wire hanger and rinse it in warm soapy water.

4. 04

   Check the pipe

   Look into the pipe that goes into the wall. If you see grease or hair, use a drain snake from there.

5. 05

   Refit

   Check the washers are in place and hand-tighten the nuts. Run the tap and look for drips.

Method 4: use a drain snake

A drain snake (or drain cleaning cable) is a flexible wire that reaches blockages beyond the U-bend. Remove the trap, feed the snake into the waste pipe and turn the handle as you push. When you feel resistance, keep turning gently to break up or hook the blockage, then pull it out and clean the cable. Flush with plenty of water. In bathroom basins, a plastic hair snare pulls hair out through the plughole without taking anything apart. If the snake stops moving, stop pushing: forcing it can damage joints.

Method 5: chemical unblockers, with care

• Use them last, after the plunger, the U-bend and the snake.
• Choose a non-corrosive product where possible, and check it suits your pipes.
• Read the label first and use the amount it gives.
• Protect yourself: rubber or plastic gloves and goggles; cotton gloves soak up the product.
• Ventilate the room.
• Never mix unblockers or cleaning products: some combinations release toxic gases. Bleach reacts with acids, including vinegar and limescale removers.
• Keep them in their original container, out of the reach of children.

How to stop your sink blocking again

• Fat, oil and grease: let them cool in a jar, a yoghurt pot or a piece of foil and put them in the bin once set.
• Wipe pans and plates with kitchen roll before washing up.
• Use a sink strainer to catch food scraps, and empty it into the bin or food-waste caddy.
• Coffee grounds go in the bin: they settle into a solid blockage.
• Clear hair from the basin plughole regularly.
• Clean the U-bend every few months if your sink tends to block.

When to call a plumber

• The sink is still blocked after you have cleaned the U-bend.
• Water comes up in another sink, bath or shower when you drain this one.
• Several plugholes are slow at the same time.
• The sink blocks again within days.
• You have used a chemical unblocker and it has not worked.
• The snake will not go any further.

A plumber or drainage company can find the blockage with a camera and clear it with high-pressure water jets.

Sources

Official and consumer guidance, checked on 25 October 2026.

• Stroud District Council · How to unblock a sink ↗Plunger, hot (not boiling) water burst and removing and cleaning the U-bend.
• Which? · How to unblock a sink ↗Water to cover the plunger cup, step-by-step U-bend cleaning, hair snares, what never to pour down the drain and when to call a professional.
• KEMI, Swedish Chemicals Agency · Drain cleaner ↗Mechanical methods first, non-corrosive products, children's safety and telling a professional which product you used.
• Consumer Council Hong Kong · Drain unblockers ↗Never mixing products, gloves and goggles, ventilation, following instructions and heat softening plastic joints.
• Poison Control (US) · What's in drain cleaner ↗Corrosive ingredients, pouring close to the drain and splash-back from a completely blocked drain.
• Thames Water · Bin it, don't block it ↗Disposing of fat, oil and grease, sink strainers and why hot soapy water does not help.
• B&Q · How to unblock a basin ↗Sealing the overflow before plunging (retailer guide, as an example).
• Hadley · Unclogging toilets and drains ↗Plunging technique and when not to plunge.