How to unblock a sink

A blocked sink is one of the most frustrating household problems. Whether it's a bathroom sink clogged with hair and toothpaste, or a kitchen sink backed up with grease and food scraps, the result is the same: standing water and foul smells.

Before you call a national chain and pay premium prices, try these DIY methods to unblock your sink. If these fail, the local experts at CleverWorks are ready to help with a professional CCTV drainage survey to pinpoint the exact cause of the problem across London.

Step 1: The Boiling Water Flush

If your sink is draining slowly but isn't completely blocked, boiling water is the simplest first step. This works particularly well in kitchen sinks where fat, oil, and grease (FOG) have started to solidify.

• Boil a full kettle of water.
• Pour it slowly and directly down the plughole in two or three stages.
• Wait a few seconds between each pour to let the hot water melt the grease.

Note: Do not use boiling water if you have PVC pipes, as the heat can soften or melt the plastic. Use hot tap water instead.

Step 2: The Plunger Technique

If boiling water doesn't work, it's time to create a vacuum. You will need a standard cup plunger.

• If you have a double sink, seal the second plughole with a wet cloth.
• Ensure there is enough water in the blocked sink to cover the rubber cup of the plunger.
• Place the plunger over the plughole, creating an airtight seal.
• Plunge vigorously up and down for about 20-30 seconds.
• Remove the plunger to see if the water drains away. Repeat if necessary.

Step 3: Clean the U-Bend (Trap)

If plunging fails, the blockage is likely trapped in the U-bend (the curved pipe beneath the sink). This is a messy job, so put on some rubber gloves and place a bucket underneath the pipe.

• Locate the U-bend under the sink.
• Carefully unscrew the two plastic connections holding the U-bend in place.
• Empty the water and debris from the U-bend into your bucket.
• Clean the U-bend thoroughly with an old toothbrush or wire brush.
• Reattach the U-bend, ensuring the seals are tight, and run the tap to check for leaks.

When to call CleverWorks for a CCTV Drainage Survey

If you have cleaned the U-bend and your sink is still blocked, the problem lies deeper within your drainage system. This is where guessing stops and professional diagnostics begin.

At CleverWorks, we use state-of-the-art cameras to conduct a CCTV drainage survey. This allows us to see exactly what is causing the blockage—whether it's a severe fatberg deep in the main line, or a collapsed pipe—without any unnecessary digging. We provide fast, fixed-price solutions across London and the UK.