Unscrew, empty and clean a blocked sink trap, then refit it and test for leaks.
ST-01Clear the cupboard and get set upEmpty the cupboard under the sink and lay an old towel on the floor. Put a bucket or washing-up bowl directly under the trap to catch water and debris. Have a torch to hand, as it's dark under there.
ST-02Identify the trap and check its typeThe trap is the curved or bottle-shaped pipe under the plughole. Most modern sinks have a bottle trap (a round pot with a screw cap on the bottom) or a U-bend trap. Both come apart the same basic way, by hand or with pliers, so don't worry which one you've got.
ST-03Loosen the slip nutsFind the large plastic nuts where the trap connects to the sink waste pipe and the wall pipe. Turn them anticlockwise by hand first. If they're too tight, use adjustable pliers or a wrench, but wrap a cloth round the nut so you don't crack the plastic.
ST-04Drain and remove the trapWater and gunk will run out as you loosen the nuts, so keep the bucket underneath. On a bottle trap, unscrew the bottom pot by hand once the nuts are loose. On a U-bend, slide the whole curved section down and off.
ST-05Clean out the blockageTip the contents of the trap into the bucket or bin. Use a bottle brush or old toothbrush to scrub out hair, grease and food debris from inside the pipe. Rinse the trap under a tap or with water from a jug until it runs clear.
ST-06Check the seals and washersLook at the rubber or plastic washers on each joint. If any are split, flattened or perished, replace them with new ones from a hardware shop, taking the old one with you to match the size.
ST-07Reassemble the trapFit the trap back together in the reverse order you took it apart. Make sure each washer sits square in its joint, then hand-tighten the nuts. Give each nut a final quarter turn with pliers, but don't overtighten as this can crack the plastic or squash the washer out of shape.
ST-08Test for leaksPut the bucket back under the trap just in case. Run the tap for a minute and check every joint by feel and eye for drips. If a joint leaks, tighten it a little more or check the washer is seated properly, then test again.
ST-09Tidy up and dispose of wasteBin the gunk from the trap in the household waste, not down the sink. Wipe down the pipework and cupboard floor, dry any splashes, and put your cleaning products back under the sink.