A blocked sink often starts as a slow drain before becoming completely clogged. Grease, food particles, soap, hair and debris can gradually restrict the waste pipe until water struggles to escape.
Some minor blockages can be cleared safely without specialist equipment. The important thing is to avoid mixing aggressive chemicals or pushing the obstruction further into the pipework.
Kitchen sinks commonly collect cooking grease, oil, food particles, coffee grounds and detergent deposits. Bathroom basins more commonly collect hair, soap, toothpaste, cosmetic residue and limescale.
A blockage can form slowly as several materials stick together inside the waste pipe.
Remove visible debris from around the plug hole. If your sink has a removable strainer, clean it thoroughly. Sometimes the restriction is immediately beneath the surface rather than deep inside the pipe.
For a kitchen sink affected by light grease, hot water can sometimes soften deposits. Do not use boiling water if your sink, waste fittings or pipework manufacturer advises against it because very hot water can damage some plastic waste components.
A sink plunger can create alternating pressure to loosen a local blockage. Cover the overflow opening with a damp cloth, add enough water to cover the plunger cup, position the plunger firmly over the drain and use several controlled pushes and pulls.
Avoid excessive force on old or fragile waste fittings.
The curved trap beneath the sink is designed to hold water and prevent drain odours entering the room. It is also a common place for debris to collect.
If the trap is accessible and you are comfortable removing it, place a bucket underneath, take a photograph before dismantling, loosen the fittings carefully, empty and clean the trap, then reassemble and check for leaks.
If the fittings are seized, damaged or leaking, stop and call a plumber.
If the trap is clear but the sink still will not drain, the blockage may be deeper in the waste pipe. Signs include water backing up into another sink, gurgling from nearby wastes, repeated blockages or more than one fixture draining slowly.
Professional drain equipment may be needed to clear the obstruction without damaging the pipework.
Chemical drain products can be hazardous and can damage some pipes, seals or finishes. Never mix different drain chemicals.
If a chemical cleaner has already been used, tell the plumber before they work on the waste pipe.
Avoid disposing of cooking oil, fat and grease, coffee grounds, rice and pasta, paint, plaster, food scraps and wet wipes down the sink.
Repeated blockages suggest the underlying cause has not been fully removed. Possible reasons include a partial blockage further down, poor waste-pipe fall, damaged pipework, grease coating the pipe or a recurring disposal habit.
Call a plumber if the sink remains blocked after basic checks, several fixtures are draining slowly, water backs up elsewhere, waste fittings leak or the blockage keeps returning.
TES Heating can investigate blocked sinks and internal waste pipework across London.
Use a sink strainer, scrape food into the bin, never pour cooking oil down the sink, clean removable strainers regularly and deal with slow drainage before it becomes a full blockage.
Hot water may help with light grease, but boiling water can damage some plastic waste fittings. Follow the manufacturer’s guidance.
A correctly used sink plunger is often suitable for minor blockages, provided the waste fittings are in good condition.
Gurgling can indicate restricted airflow or a partial blockage in the waste system.
The obstruction may be further down the pipe or the waste system may have another flow problem.
Use caution and follow the product instructions. Never mix different chemicals, and tell your plumber if chemicals have been used.
