A kitchen or bathroom sink that drains slowly is nearly always a build-up of grease, soap and hair just inside the waste - not a drain problem. Most blockages clear with things you already have at home, and it is worth working through them in order before paying for a call-out.
Before anything else, bail out the standing water so whatever you try next is working on the blockage, not the puddle.
Try These In Order
For a grease-clogged kitchen sink, a kettle of just-boiled water poured straight down often melts the blockage. Skip this on plastic wastes if unsure - use hot tap water instead.
Cover the overflow with a wet cloth, put a cup plunger over the plughole and give it ten firm pumps. The seal is what makes it work.
Tip a few tablespoons of baking soda down, then a cup of white vinegar. Leave it fizzing for fifteen minutes, then flush with hot water.
Put a bucket under the U-bend, unscrew it by hand, and pull out the gunk. This is where most blockages actually sit.
If It’s Further Down
- A drain snake or even a straightened wire coat hanger can hook out hair just past the trap
- Avoid chemical drain cleaners where you can - they are harsh on pipes and seals and often only punch a hole through the blockage
- If two or more fittings are slow at once, the blockage is in the shared waste, not the sink
Stop It Coming Back
- Never pour fat or oil down the sink - let it set and bin it
- Fit a cheap drain strainer to catch food and hair
- Run hot water for a few seconds after washing up greasy pans
- Flush the trap through with hot water and a little washing-up liquid now and then
When to Call a Plumber
If you have cleared the trap and plunged it and the water still will not go down, or if several sinks and the toilet are draining slowly together, the blockage is in the main waste or drain rather than the sink - and that needs proper equipment. Water backing up into other fittings, or a foul smell with it, is a sign to stop and get help.
A drain blockage beyond the sink is priced in our blocked drain cost guide, and the emergency plumber cost guide covers call-out rates. If it is overflowing or backing up badly, get an emergency plumber on the way.