How to Unblock a Sink Without Chemical Drain Cleaner

Chemical drain cleaner is sodium hydroxide, and it works by generating heat while dissolving organic matter. It also degrades rubber seals, can damage older pipework, and if it fails to clear the blockage you now have a pipe full of caustic liquid that you have to work on anyway.

There are three mechanical methods. Try them in this order.

Method one: the plunger, done correctly

Most people plunge wrongly, which is why they conclude it does not work.

1. Block the overflow. Every basin has one, usually a slot near the rim. Stuff a wet cloth firmly into it. Without this, you are pushing air out of the overflow rather than pressure down the pipe.
2. Add water until the plunger cup is fully submerged. Plunging air achieves nothing — water is incompressible and transmits the force.
3. Seat the plunger flat and press down slowly to expel the air underneath.
4. Pump sharply, twenty times, keeping the seal intact throughout. The pull stroke matters as much as the push.
5. Break the seal and check. Repeat twice more before concluding it has failed.

Method two: clean the trap

The U-bend under the sink catches almost everything. On modern plastic waste systems it unscrews by hand.

1. Put a bucket underneath. It will be full of water and the water will be unpleasant.
2. Unscrew the two collars either side of the U. Hand-tight is how they were fitted, so hand pressure should undo them. Water pump pliers with a cloth wrapped round help if they are stiff.
3. Remove and empty the trap. In a kitchen sink expect solidified fat and food. In a bathroom basin expect a compacted plug of hair and soap.
4. Clean it out with a bottle brush and hot soapy water.
5. Check the O-rings before reassembly. If one is cracked or flattened, replace it — they cost almost nothing and are the usual cause of the drip that appears after this job.
6. Reassemble hand-tight only. Spanners crack plastic collars.

Method three: a drain auger

A hand auger — a coiled spring on a reel — costs about the same as three bottles of chemical cleaner and lasts forever.

Feed it into the pipe with the trap removed, turning the handle clockwise as you push. When it stops, keep turning; you are either boring through the blockage or hooking it. Withdraw slowly and expect to pull out something horrible.

What actually blocks each drain

• Kitchen sinks — fat. It pours in liquid and sets solid on the cold pipe walls, then catches everything else. Never pour cooking fat down a drain, even followed by hot water; it simply solidifies further along where it is harder to reach.
• Bathroom basins — hair bound with soap scum into a felt-like mat.
• Showers — the same, usually just below the grate and reachable with a bent wire.
• Toilets — wet wipes, essentially always, regardless of what the packet claims about flushability.

Keeping them clear

Once a month, pour a kettle of boiling water down the kitchen sink slowly. It melts fat before it accumulates.

For bathroom drains, a plastic drain claw — a thin barbed strip — costs almost nothing and pulls the hair mat out in seconds. Doing this quarterly means you will essentially never need any of the methods above.