How do you clear a blocked sink?

Start with simple checks

A sink may drain slowly because the plug strainer is clogged, the trap is obstructed or the drain beyond it is restricted. Clear visible debris from the plughole using gloves. If more than one fixture is backing up or you notice sewage smells, the problem may be further along the drainage system.

Do not pour boiling water into a sink with plastic fittings or a fragile basin. Do not mix chemical drain cleaners, bleach or other products. They can react dangerously and may remain in standing water, exposing anyone who later opens the trap.

Try a plunger

1. 1Remove standing water until the plunger cup can sit over the plughole. If there is an overflow, cover it with a damp cloth to help create a seal.
2. 2Place the plunger over the waste and press gently first to expel air, then pump steadily while keeping the cup sealed.
3. 3Lift the plunger and check whether water drains. Repeat a few times if needed, then run a small amount of water to test.
4. 4Stop if water rises in another fixture, there is a strong sewage smell, or the blockage does not shift.

When to check the trap

A bottle trap beneath the sink may be removable for cleaning, but only attempt this if there are no caustic chemicals in the water and you can catch the contents safely. Put a bucket underneath, use gloves and refit seals in their original position. If the trap is corroded, inaccessible or you are unsure how it comes apart, leave it to a plumber.

A blockage that returns can indicate a build-up deeper in the waste, poor pipe fall or a damaged pipe. Do not push sharp objects down the drain; they may puncture pipework or become stuck. TraceFix can investigate persistent sink blockages in Birmingham and London.