How to unblock a kitchen sink or basin

Most blocked sinks and basins are blocked within arm's reach: in the plughole, the overflow or the trap directly underneath. Start there, with simple tools from a basic plumbing tool kit, before reaching for chemicals. A bath is plumbed differently, with a shallow trap hidden behind the panel; see bath panels and traps.

First, find out how far it goes

• One sink or basin is slow, everything else drains fine: the blockage is almost certainly in that fitting's waste or trap. Carry on with this guide.
• The kitchen sink and the washing machine or dishwasher both back up: they often share a trap or waste pipe, so it is still likely to be close by.
• Several fittings are slow, the toilet gurgles when the sink drains, or water comes up in a downstairs shower or outside gully: the blockage is further down, in the main waste pipe (the stack) or the drain. See "When to call a plumber" below.

Clear the plughole

Kitchen sinks block with fat, food and coffee grounds. Basins block with hair, soap and toothpaste.

1. Lift out or unscrew the plug or strainer if it comes out. Many pop-up basin plugs lift or twist out.
2. Pull out hair and debris with gloved fingers or a cheap plastic hair-catching strip.
3. Run hot water from the tap to see if it clears. Do not pour boiling water into a plastic waste or onto a ceramic basin.

Use a plunger properly

A plunger works by pushing and pulling a column of water, so it needs a seal.

1. Leave a few centimetres of water in the bowl, enough to cover the plunger cup.
2. Block the overflow. On a basin, hold a damp cloth firmly over the overflow slot. On a double kitchen sink, put the plug in the other bowl and hold it down. Otherwise the pressure escapes there.
3. Seat the cup over the plughole and pump firmly up and down a dozen or so times, keeping the seal, then pull off sharply.
4. Repeat a few times. If the water drops away with a gurgle, run the hot tap for a minute.

If the sink has a dishwasher or washing machine hose on its waste, check the hose is clipped and will not blow off when you plunge.

Take off and clean the trap

The trap is the bend under the sink that holds water to stop drain smells coming back up. In UK homes it is usually a plastic bottle trap (a cylinder with a screw-off base) or a P-trap or U-bend with two screw nuts. Kitchen traps are commonly 40mm; basin traps are commonly 32mm. Our guide to basin wastes and bottle traps explains the parts.

1. Put a bucket or washing-up bowl underneath and a towel round it. The trap is full of dirty water.
2. Unscrew the trap nuts or the bottle base by hand. They are plastic. If one is stuck, use grips gently, with a cloth to protect it.
3. Empty it into the bucket and clean out the gunk. Look into the pipe each side and pull out anything you can reach.
4. Check the rubber or plastic seals are in place, refit by hand, and run water while you watch for drips.

If a trap is cracked, or a seal has perished, replacement plastic traps are cheap. Match the size (32mm or 40mm), the type and the depth of water seal, and whether it needs a spigot for an appliance hose. Do not use PTFE tape on plastic waste trap threads: they seal on the washer.

Chemical drain cleaners: be careful

Drain cleaners can be strongly caustic or acidic. If you use one:

• read the label and follow it exactly, with gloves and eye protection;
• never mix two products, or follow one with another, and do not use bleach alongside. Mixing cleaners can give off dangerous fumes or react violently;
• do not plunge or take off the trap after putting a chemical in. It can splash out at you. Tell anyone else who might work on the sink, including a plumber, what you used;
• check the product is suitable for your pipes and any septic tank.

A chemical will not shift a solid object like a bottle cap or a ring, and often only part-clears a fat blockage.

Stopping it happening again

• Wipe fat and food off pans into the bin before washing up. Do not pour fat down the sink, even with hot water.
• Use a sink strainer in the kitchen and a hair catcher in the basin.
• Clean the trap every so often if you have a busy kitchen sink.

When to call a plumber or drainage company

• the blockage is past the trap and you cannot reach it;
• more than one fitting is affected, or a toilet gurgles when the sink empties (see unblocking a toilet);
• there is water coming up from a drain outside, or a smell of sewage;
• the waste pipe is leaking inside a wall or under a floor. If the leak is on a supply pipe rather than a waste, see finding a leak and the stopcock.

Pipes shared with neighbours and the public sewer are often the water company's responsibility rather than yours. If the problem looks like it is outside your property, contact your water company first. Our outside drains guide explains gullies, manholes and who owns what.

Sink parts and tools at Wickes

We haven't tested this. Figures are as the maker states them (checked 13 November 2026).

Why does my sink still drain slowly after plunging?

The overflow may not have been sealed, or the blockage is in the trap or beyond. Take the trap off and clean it.

Is it safe to use a plunger after drain cleaner?

No. It can splash the chemical back at you. Wait and follow the product label, or call a plumber and tell them what you used.

Can I use a toilet plunger on a sink?

A cup plunger works on both, but keep a separate one for the sink if you can, for hygiene.