Blocked Drain? What to Do Right Now, Step by Step

What should I do first when a drain is blocked?

Stop running water into the blocked sink, bath, shower or toilet straight away. Every extra litre raises the risk of an overflow, and if the blockage is in the underground drain, water from other fittings can come back up at the lowest point in the house.

Then take a moment to get ready:

• Put on rubber gloves, and ideally eye protection if you may use a plunger on a sink.
• Lay old towels around the fitting.
• Keep children and pets away from the area.
• Open a window if there is a smell.

How do I know where the blockage is?

Check whether one fitting is affected or several. This single check tells you most of what you need to know.

• Only one sink, bath or toilet is slow: the blockage is probably in that fitting, its trap or its short waste pipe. This is often something you can clear yourself.
• Several fittings are slow, or a toilet gurgles when you run the bath: the blockage is likely further down, in the shared waste pipe or the underground drain.
• Water is coming up from an outside gully or a manhole cover: the underground drain is blocked.

If it looks like an underground drain problem, skip to the section on when to call a professional. DIY rarely fixes those, and pushing more water down makes things worse.

What are the safe DIY steps, in order?

For a blocked sink, bath, shower or toilet, work through these steps from the gentlest to the most hands-on. Stop as soon as the water drains freely.

1. Remove what you can see

With gloves on, lift out the plug or strainer and clear any hair, food or soap build-up you can reach. In showers and baths, hair caught just below the plughole is one of the most common causes.

2. Use a plunger

A plunger is the most effective household tool for a local blockage. Use a cup plunger for sinks and baths and a flange plunger for toilets.

1. Block the overflow hole with a damp cloth so the pressure goes down the pipe.
2. Make sure there is enough water to cover the plunger cup.
3. Push down gently first to push the air out, then plunge firmly up and down 10 to 15 times.
4. Lift off and see if the water drains. Repeat a few times if needed.

3. Try hand-hot water and washing-up liquid

For greasy kitchen sinks, a good squeeze of washing-up liquid followed by a kettle of hot water (not boiling) can loosen fat. Avoid boiling water in toilets, as it can crack porcelain, and on plastic waste pipes, where it can soften joints.

4. Clean the trap

Most sinks have a U-bend or bottle trap under the basin that unscrews by hand. Put a bucket underneath, unscrew it slowly, empty it and rinse it out, then refit it firmly and run water to check for leaks.

5. Clear an outside gully

If a gully outside your back door is overflowing, the blockage may be in the grated trap itself. With thick gloves, lift the grate and scoop out leaves, food and fat into a bag. If water still won’t go down, the problem is deeper in the drain.

What should I never do with a blocked drain?

Some common fixes make blockages worse or are genuinely dangerous. Avoid the following:

• Never mix chemical drain cleaners. Different products can react together and release harmful fumes or heat. Never pour one product on top of another.
• Don’t use chemicals after plunging, or plunge after using chemicals. Plunging can splash caustic liquid onto your skin and eyes.
• Don’t keep flushing a blocked toilet. One flush to test is enough; more risks an overflow.
• Don’t push wire coat hangers deep into pipes. They can scratch fittings and pack the blockage tighter.
• Never climb into a manhole or inspection chamber. They can contain harmful gases and are not safe to enter.
• Don’t pour fat, oil or grease down the sink to “flush it through”. It sets in the pipes and builds up over time.

If you have already used a chemical cleaner and it hasn’t worked, tell whoever comes to clear the drain so they can take precautions.

When should I stop and call a professional?

Stop DIY and get professional help if any of the following apply:

• Two or more fittings are blocked or slow at the same time.
• Sewage or dirty water is coming up into a shower, bath, toilet or floor drain.
• An outside manhole or gully is overflowing.
• You’ve tried plunging and cleaning the trap and nothing has changed.
• There is a persistent sewage smell inside or outside.
• The same drain keeps blocking every few weeks.

These usually point to a blockage in the underground drain, or to a damaged pipe. A drainage engineer can clear it with mechanical rodding or high-pressure water jetting, and if it keeps coming back, a CCTV drain survey can show why.

If sewage is backing up into your home, avoid touching it, keep everyone away from the area and call a professional promptly. Basement and lower-ground-floor flats, common across London, tend to be the first place backed-up water appears.

Is the blockage my responsibility?

Blockages in your own fittings and in drains that serve only your property within your boundary are usually your responsibility, or your landlord’s if you rent. Shared drains and pipes beyond your boundary are generally Thames Water’s. If you’re unsure, lifting an inspection chamber cover (with gloves, and never climbing in) can show whether the blockage is in your section of pipe.

How can I stop it happening again?

Most household blockages come from what goes down the drain. A few habits make a real difference:

• Only flush pee, poo and toilet paper. Wipes labelled “flushable” often don’t break down.
• Let fat, oil and grease cool, then scrape it into the bin rather than the sink.
• Use sink strainers and a plughole hair catcher.
• Keep outside gullies clear of leaves, especially in autumn.

Need help with a blocked drain?

If DIY hasn’t worked, Pipe & Drain Cleaners can help with blocked drains, toilets and sinks across London, from Hackney to Wandsworth. You’ll get a fixed quote before any work starts. Call 0800 470 0946 24/7, or book online.

Frequently asked questions