How to Unblock a Drain — Methods That Actually Work

Most blocked drains can be cleared at home with tools you already have, in under half an hour. The trick is using the right method for the type of blockage. This guide walks through the methods that actually work, in the order you should try them, and explains when to stop and call a plumber.

Step 1: Identify what's blocked

Before reaching for chemicals or tools, work out the scope of the blockage:

• Single fixture slow (one sink, one shower): Localised blockage in the trap or branch pipe. Most likely cleared with DIY methods.
• Multiple fixtures slow on the same level: Blockage in the shared horizontal pipework. May need a drain snake or professional jetting.
• Multiple fixtures slow on different levels, or toilet backing up: Main drain blockage or external drain issue. Usually professional only.
• Overflowing external manhole or surface water issues: Main sewer drain — almost always professional jetting.

If anything beyond a single fixture is affected, the problem is bigger than DIY. Don't waste time pouring chemicals down — call a plumber.

Method 1: Boiling water (free, 5 minutes)

For sinks blocked with grease, fat, or soap scum:

1. Boil a full kettle
2. Pour slowly down the drain in three or four stages
3. Wait 30 seconds between pours to let the water work on the blockage
4. Test by running cold water

Don't use boiling water on PVC pipes if the blockage is suspected to be in older plastic pipework — sustained heat can soften and damage them. For kitchen sinks with copper or modern uPVC plumbing, boiling water is safe and surprisingly effective.

Method 2: Plunger (£5, 5 minutes)

A standard cup plunger works on sinks, basins, baths, and toilets. The technique:

1. For sinks/baths: cover any overflow with a wet cloth to maintain seal
2. Ensure enough water in the basin to cover the rubber cup
3. Place the cup directly over the plughole
4. Push down firmly to compress the air, then pull up sharply
5. Repeat 10–15 times in rapid succession
6. Test by running water

For toilets, use a flange plunger (the type with a soft rubber extension) — same technique, but extra care to ensure a good seal at the bottom of the bowl.

Method 3: Bicarbonate of soda and vinegar (free, 30 minutes)

The classic kitchen chemistry method, more effective than you might expect:

1. Pour half a cup of bicarbonate of soda down the drain
2. Follow with half a cup of white vinegar
3. Cover the drain with a plug or wet cloth to keep the reaction down the pipe
4. Wait 30 minutes
5. Flush through with a kettle of hot water

This works well on slow drains caused by organic build-up (hair, soap scum, food particles). It won't clear physical obstructions like wet wipes or solid objects.

Method 4: Drain snake / auger (£10–£30, 15 minutes)

A flexible drain snake reaches blockages deeper in the pipework that water and chemicals can't touch:

1. Remove the trap under the sink if possible (place a bowl underneath)
2. Feed the snake into the pipe slowly
3. Rotate the handle as you advance
4. When you feel resistance, work the snake back and forth to break up the blockage
5. Withdraw slowly, pulling out any debris you've caught
6. Refit the trap and test

Snakes 3–5 metres long cover most household drains. For longer reaches you'll need a longer professional auger.

Method 5: Check the external drain (free, 10 minutes)

If multiple internal drains are slow, lift the external inspection chamber cover at the boundary of your property. The chamber is a concrete or plastic box with a metal lid, usually labelled with a flow direction arrow.

Look inside:

• If the chamber is empty, the blockage is between the house and this chamber — internal problem
• If the chamber is full of water, the blockage is downstream — between this chamber and the sewer main
• Multiple chambers full means the issue is in the public sewer — contact Anglian Water on 0345 714 5145 (they have responsibility for sewers beyond your property boundary)

If the chamber has accessible debris near the top — leaves, wipes, silt — remove with a gloved hand or drain rod and check if the flow restores.

What not to try

• Caustic chemical drain cleaners on suspected solid blockages — they don't dissolve plastic or hair effectively and create hazardous splashback if the blockage doesn't clear
• Multiple methods mixed together — chemicals and water react unpredictably; never mix bleach with anything containing ammonia
• Wire coat hangers as DIY snakes — they can damage trap seals and get stuck
• Removing toilet pans to investigate — toilets need re-sealing properly afterwards or you'll have leaks

When to call a plumber

• Multiple drains blocked simultaneously
• DIY methods unsuccessful after two attempts
• Sewage smell or sewage backing up indoors
• Toilet not flushing even after the cistern fills
• External chamber full or overflowing
• Persistent recurring blockages (suggests a structural drain issue)

Our drain blockage team covers Peterborough and surrounding PE postcodes with professional jetting equipment and CCTV inspection if needed. Most domestic blockages are cleared in under 90 minutes. See also our guide on signs of a blocked drain for spotting issues before they become emergencies.