Use this guide when a sink drains slowly or not at all. You will need rubber gloves, a sink plunger, a bucket, old towels and, if needed, a plastic drain snake or wire.
Step by step
Clear what you can see
Put on gloves and remove anything visible in the plug hole, such as food scraps or hair. Unscrew or lift out the plug or strainer if it comes out, and clean it. Bail out standing water into a bucket so you can work.
Try hot water
Pour a kettle of hot, not boiling, water slowly down the drain. This can soften grease and soap near the plug hole. Wait a few minutes to see whether the water level drops.
Use a plunger properly
Block the overflow hole with a damp cloth, and on a double sink block the other plug hole too, so the pressure goes down the drain. Leave a few centimetres of water in the sink to cover the plunger cup. Pump firmly up and down ten to fifteen times, then lift off quickly and check the flow.
Clean the trap
Place a bucket and towels under the U-shaped or bottle trap under the sink. Unscrew the trap by hand, empty it into the bucket and clean it out with an old brush. Check the washers are seated, then screw it back on hand-tight and run water to check for leaks.
Use a drain snake if needed
If the trap was clear, the blockage is further along the waste pipe. Feed a plastic drain snake or flexible wire into the pipe where the trap connects, twisting as you go, and pull back any debris. Refit the trap and flush with hot water.
Ready-to-use checklist
- Gloves on and visible debris removed
- Standing water bailed out
- Overflow and second plug hole blocked before plunging
- Bucket and towels under the trap
- Trap cleaned and washers checked
- Trap refitted hand-tight and checked for leaks
- Sink draining freely
Practical tips
- Wipe greasy pans with kitchen paper before washing up, as fat poured down the sink is a common cause of blockages.
- Fit a simple sink strainer in kitchen and bathroom plug holes to catch food and hair.
- Avoid mixing different drain products, and never use a plunger after pouring chemicals down, as they can splash back.
Common problems
Several sinks, the bath and the toilet are all slow at once.
This suggests a blockage in the main drain rather than one sink. Contact your water company, as they are often responsible for shared sewers, or a drainage specialist if it is on your private pipework.
The trap leaks after I put it back.
Check the rubber washers are in place, not twisted, and the threads are not cross-threaded. Undo it, reseat the washers and screw it back on straight and hand-tight, with a little extra turn if needed.
The sink smells bad even though it drains.
Clean the trap and the overflow channel, which collects grime, and run hot water through regularly. If the smell persists, a plumber can check whether the trap seal is being siphoned or the waste pipe lacks ventilation.