Fix a gurgling sink

Clear a gurgling sink by cleaning the trap, checking the air valve and clearing the waste pipe.

GS-01Set up and protect the areaClear everything out from under the sink so you can see the pipework. Lay an old towel on the cabinet floor and put a bucket under the trap — the U-shaped pipe just below the sink. This catches any water and gunk when you open things up.

1 each · Bucket

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1 each · Old towel or rags

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1 pair · Rubber gloves

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GS-02Work out when the gurgling happensRun the tap and watch the sink drain. If it gurgles as the water goes down, the trap or the pipe just after it is the likely cause. If it gurgles when a washing machine, dishwasher or another sink drains nearby, the problem is more likely a blocked or missing air admittance valve, or a blockage further down the shared waste pipe.

GS-03Empty and clean the trapWith the bucket underneath, loosen the two slip nuts on the trap by hand, or with an adjustable spanner if they're tight. Slide the trap down and tip out the water and debris into the bucket. Clean it out with an old toothbrush or bottle brush and warm soapy water, and check the rubber washers inside aren't cracked or flattened.

1 each · Adjustable spanner

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1 each · Old toothbrush or bottle brush

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1 set · Replacement trap washers

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GS-04Check the air admittance valve (AAV)Look for a small dome-shaped valve on the waste pipe near the sink, or lower down where pipes join a main stack. This lets air into the system so water doesn't get siphoned out of the trap, which is what causes gurgling. Unscrew it, check for debris inside, and give it a gentle shake — you should hear or feel it move freely. If it's stuck, cracked, or silent, replace it.

1 each · Air admittance valve (AAV)

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GS-05Clear the waste pipe if the gurgling continuesIf the trap and AAV are both fine, the blockage is likely further along the waste pipe. Feed a plumber's snake or drain auger through the open trap connection, turning it gently as you push, to break up or pull out any build-up. Never force it — if it won't move, stop and try from a different access point, such as a rodding eye if one is fitted.

1 each · Plumber's snake / drain auger

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GS-06Reassemble the trapSlide the trap back into place and hand-tighten the slip nuts, then add a quarter turn with the spanner. Don't overtighten — plastic fittings crack easily and a firm hand-tight fit with a small nip is usually enough. Fit the AAV back on if you removed it, pushing it in firmly until it seats.

GS-07Test for leaks and gurglingRun the tap for a minute and check every joint on the trap for drips, wiping each one dry and checking again after a few minutes. Then run the tap once more, or run a nearby appliance if that was the trigger, and listen for gurgling. If it's gone, you've fixed it.

GS-08Tidy upBin the debris from the trap rather than putting it back down the sink. Wash out the bucket and tools, wipe the inside of the cabinet dry, and put everything you moved back in place.

500 ml · White vinegar (for a final clean-through)

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