Most blocked sinks can be cleared in under half an hour without calling anyone out. Start with a plunger, sealing the overflow with a damp cloth. If that does not work, put a bowl underneath, unscrew the trap and clean it out by hand. A drain rod or hand auger can reach blockages further along the waste pipe. If several sinks, the bath or the toilet are slow at the same time, the blockage is probably in the main drain rather than your sink.
Before you start
- Do not pour boiling water down a blocked sink. It will not dissolve fat, and very hot water can soften or distort plastic traps and joints.
- If you have already used a chemical unblocker, do not plunge or open the trap until you have flushed it through as the label describes. Wear gloves and eye protection, because caustic water can splash back.
- Clear the cupboard under the sink and have a bowl or bucket, old towels and rubber gloves ready.
Step 1: use a plunger
- Remove the plug and any sink strainer.
- Block the overflow with a damp cloth held firmly in place. On a double sink, block the second plughole too. Without this, the pressure escapes and the plunger cannot do its job.
- Leave enough water in the bowl to cover the cup of the plunger.
- Seat the plunger over the plughole and pump firmly up and down ten to fifteen times, keeping the seal. Then pull it away sharply.
- Repeat a few times. If the water starts to drain, run hot tap water for a minute to clear any loose debris.
Step 2: clean the trap
The trap is the curved or bottle-shaped section of pipe directly under the plughole. It holds a small amount of water to stop drain smells coming back, and it is where most blockages collect.
- Put the bowl directly under the trap.
- Unscrew the plastic nuts by hand. On a bottle trap, unscrew the bottom section. On a tubular P or U trap, undo the nuts at both ends.
- Empty the water and debris into the bowl, then clean the trap with an old brush. Check the short pipes either side for build-up.
- Check the rubber washers and seals are seated and not split. Replacement waste parts are in plumbing parts and spares.
- Refit the trap and tighten the nuts by hand until snug. Do not overtighten plastic nuts, as this can distort the washer.
- Run the tap and check for drips underneath.
Step 3: clear the waste pipe
If the trap was clear but the sink still will not drain, the blockage is further along the waste pipe. With the trap removed, feed a flexible drain rod or hand auger into the pipe, turning it as you go, until you feel the blockage. Work it back and forth to break it up, withdraw it, then refit the trap and flush with plenty of water. Browse hand tools and drainage for rods and accessories.
Using chemical drain unblockers
Chemical unblockers can shift soap and hair build-up, but they need care.
- Read and follow the label, including the safety warnings and how long to leave it.
- Never mix different products, and never use one straight after another.
- Do not use them in a sink full of standing water unless the label allows it, and do not plunge afterwards.
- Check the product is suitable for your pipe material.
Cleaning products are in cleaning.
When the problem is further down
The waste from your sink joins other pipes before reaching the drain. Signs that the blockage is beyond your sink include:
- more than one fixture draining slowly at the same time;
- gurgling from the sink when the toilet is flushed or the bath empties;
- water backing up from an outside gully or a manhole near the house.
Drains that serve only your property are usually your responsibility. Since 2011, most shared drains and lateral drains in England and Wales that connect to the public sewer have been the responsibility of the water company, so if a shared drain or public sewer is blocked, contact your water company. If you are not sure who is responsible, ask them.
Stopping it happening again
- Keep fat, oil and grease out of the sink. Yorkshire Water advises letting cooking fat cool and solidify, then scraping it into the bin. It hardens in pipes and sewers.
- Fit a sink strainer to catch food scraps in the kitchen and hair in the bathroom.
- Wipe greasy pans with kitchen roll before washing them.
- Check the dishwasher and washing machine waste connections occasionally, as lint and food can build up where they join the sink waste.
If you are replacing a damaged trap or the whole waste, see above ground drainage for traps and waste pipe. If you need to remove the sink or tap to reach the waste, turn off the supply first; our guide to isolation valves explains how.
Frequently asked questions
Why does my sink smell even after unblocking it?
Debris left in the trap or waste pipe can still smell. Clean the trap thoroughly, check the overflow channel, and make sure the trap holds water. A trap that empties itself can let drain smells through.
Is it safe to use bicarbonate of soda and vinegar?
It is a gentle cleaning method and harmless to pipes, but it is unlikely to clear a solid blockage. A plunger or cleaning the trap is more effective.
Can boiling water unblock a sink?
It is not recommended. Boiling water does not dissolve fat, and it can damage plastic traps and joints. Hot tap water is fine for flushing once the blockage has cleared.
When should I call a plumber?
If the trap and the first section of waste pipe are clear but the sink still will not drain, if more than one fixture is affected, or if there is a leak you cannot stop by refitting the trap.