How to Unblock a Sink

Why Sinks Block Up

Kitchen sinks usually block due to a build-up of grease, food scraps and soap residue. Bathroom sinks typically clog with hair, soap scum and toothpaste. Over time these substances coat the inside of the pipe and gradually narrow the opening until water cannot pass through.

Method 1: Boiling Water

The simplest fix for a slow-draining sink. Boil a full kettle and pour it directly down the plughole in two or three stages, waiting a few seconds between each pour. The heat can dissolve grease and soap build-up.

Important: Only use boiling water on metal or ceramic pipes. If you have plastic waste pipes, use hot (not boiling) water to avoid softening the joints.

Method 2: Baking Soda and Vinegar

This natural method works well for partial blockages.

1. Remove any standing water from the sink
2. Pour half a cup of baking soda down the drain
3. Follow with half a cup of white vinegar
4. Cover the plughole with a wet cloth to contain the fizzing
5. Wait 15-30 minutes
6. Flush through with hot water

The chemical reaction helps break down organic material inside the pipe.

Method 3: Plunger

A sink plunger is one of the most effective tools for clearing blockages.

1. Fill the sink with a few centimetres of water
2. Block the overflow hole with a wet cloth (this is essential for creating suction)
3. Place the plunger firmly over the plughole
4. Pump up and down vigorously 15-20 times
5. Pull the plunger away sharply
6. Repeat if needed

Make sure you use a cup plunger designed for sinks, not a flange plunger meant for toilets.

Method 4: Clean the Trap

The U-bend trap under the sink catches debris and is often where blockages form.

1. Place a bucket underneath the trap to catch water
2. Unscrew the trap by hand or with a wrench (turn anti-clockwise)
3. Empty the contents into the bucket
4. Clean the inside of the trap thoroughly
5. Check the pipe going into the wall for blockages too
6. Reassemble and run water to check

Method 5: Drain Snake

For blockages deeper in the pipe, a drain snake (also called a drain auger) can reach further than other methods.

1. Feed the snake into the plughole or the pipe behind the trap
2. Turn the handle clockwise as you push it forward
3. When you feel resistance, you have reached the blockage
4. Keep turning to break through or hook the debris
5. Pull the snake out slowly and clean it
6. Flush the drain with hot water

How to Prevent Future Blockages

• Never pour cooking oil or grease down the sink
• Use a drain strainer to catch food scraps and hair
• Run hot water down the drain after each use
• Clean the plughole weekly by removing visible debris
• Once a month, flush with baking soda and hot water

When to Call a Professional

Call a plumber if:

• None of the above methods work
• Multiple drains are blocked at the same time (this may indicate a main drain issue)
• You notice foul smells coming from the drain
• Water is backing up into other sinks or the bath
• You can hear gurgling from other drains when running water

Our plumbing service handles all types of drain blockages across South London, from simple sink clears to main drain investigations. We cover Battersea, Brixton, Tooting, Streatham and surrounding areas.