A blocked drain is one of those problems that always seems to happen at the worst time. The good news is that most blockages can be cleared at home, without a plumber, using tools and ingredients you likely already have. This guide walks through exactly how to unblock a drain, whichever room it is in, and when it is time to call in a professional.
How Do You Unblock a Drain?
To unblock a drain, first remove any standing water and visible debris, then try a plunger, followed by a baking soda and vinegar solution flushed with hot water, and finally a drain snake if the blockage remains. Working through these methods in order, from gentlest to most forceful, clears the vast majority of household blockages without needing a plumber.
What Causes a Blocked Drain?
Most blockages build up gradually rather than happening all at once. In kitchens, grease, food particles, and coffee grounds are the usual culprits, since fat solidifies as it cools and traps other debris against pipe walls. In bathrooms, hair combined with soap scum is the most common cause, since the two bind together into a dense mass that is hard to flush through with water alone. Outdoor drains often block from leaves, silt, or, in older properties, tree roots growing into ageing pipework.
Signs Your Drain Is Blocked
- Slow drainage: water taking longer than usual to disappear is often the first sign of a building blockage.
- Unpleasant smells: trapped debris begins to decompose, producing musty or sewage-like odours.
- Gurgling sounds: air trapped behind a blockage can cause a gurgling noise as water tries to pass.
- Water backing up: in a severe blockage, water may rise back up through a nearby plughole when you run a different tap.
How to Unblock a Drain: Step by Step
1. Remove Standing Water and Debris
Bail out any standing water with a cup or small container, and clear away any visible debris from the plughole by hand, wearing rubber gloves. This makes the following steps far more effective.
2. Try a Plunger
Fill the sink with enough water to cover the plunger’s cup, forming a tight seal over the drain. Pump vigorously for around 20 seconds. A few firm plunges are often enough to dislodge blockages caused by food particles or light grease. For a double sink, block off the second drain with a wet cloth first, so the pressure is not lost through the other side.
3. Use Baking Soda and Vinegar
Pour around half a cup of baking soda down the drain, followed by half a cup of white vinegar. The mixture will fizz as the chemical reaction breaks down grease, soap scum, and organic buildup. Leave it to sit for at least 15 minutes, or overnight for a stubborn blockage, then flush through with a kettle of boiling water.
4. Try Soda Crystals for Grease
Soda crystals work particularly well on grease and soap scum, though they have limited effect on hair. Dissolve a handful in a jug of hot water, pour it down the drain, and leave for at least an hour before flushing with more hot water.
5. Check the U-Bend
If the sink is still blocked, the problem may be trapped debris in the U-bend beneath it. Place a bucket underneath to catch water and debris, then carefully unscrew the trap. The U-bend is designed to hold a small amount of water permanently, so expect some spillage. Clear out any trapped material by hand, then reassemble and test with running water.
6. Use a Drain Snake
For a blockage further down the pipe, a drain snake, a flexible coil that you feed into the drain and twist to catch debris, can reach further than a plunger or chemical solution. Use a snake with a cable around a quarter to five-sixteenths of an inch to avoid damaging the pipe, and work it in gently rather than forcing it.
7. Try a Wire Hook for Hair Blockages
A straightened wire coat hanger with one end bent into a small hook can pull out hair-based blockages directly. Push it through the plughole and fish gently, working the debris up rather than pushing it further down, since forcing it deeper can make the blockage worse.
8. Use a Shop-Bought Drain Unblocker as a Last Resort
Chemical drain unblockers can clear stubborn grease, oil, or soap buildup, but always follow the product instructions and wear gloves and eye protection. Avoid bleach where possible, since repeated use of harsh chemicals can damage older pipework over time.
Which Method Works Best for Which Blockage?
| Blockage type | Best first method | Backup method |
|---|---|---|
| Grease and food debris (kitchen) | Boiling water then baking soda and vinegar | Soda crystals |
| Hair and soap scum (bathroom) | Wire hook or plunger | Drain snake |
| Foreign object | Plunger | U-bend removal |
| Deep or persistent blockage | Drain snake | Professional CCTV drain survey |
What Not to Pour Down Your Drain
Cooking fat and oil, coffee grounds, eggshells, and wet wipes are among the most common causes of repeat blockages, since fat solidifies inside pipes and wipes do not break down the way toilet paper does. Pouring these into a food waste bin or general rubbish rather than down the sink is one of the simplest ways to prevent future blockages.
When to Call a Plumber
If you have worked through the steps above and the drain is still blocked, or the same drain keeps blocking repeatedly, it is worth calling a plumber rather than escalating to stronger chemicals. A standard call-out for a blocked drain in the UK typically costs between £80 and £180, rising if a CCTV drain survey is needed to identify a deeper problem such as a collapsed pipe or tree root intrusion. Persistent blockages in the same spot, especially in an older property, can point to a structural issue that DIY methods will not resolve.
If a blocked drain is part of a wider bathroom issue, our guide to fixing a dripping tap covers another common DIY plumbing job worth tackling at the same time.
Frequently Asked Questions
How do you unblock a badly blocked drain?
Work through methods in order of force: clear visible debris first, then try a plunger, followed by baking soda and vinegar, then a drain snake. If none of these clear it, a professional CCTV drain survey can identify a deeper structural cause.
How much does it cost to unblock a drain in the UK?
A standard plumber call-out for a blocked drain typically costs between £80 and £180, with prices rising if specialist equipment or a CCTV survey is needed to locate the blockage.
Is baking soda and vinegar actually effective on blocked drains?
Yes, for grease, soap scum, and organic buildup. It is less effective against dense hair blockages or foreign objects, which usually need a physical method such as a wire hook or drain snake.
Can I use bleach to unblock a drain?
Bleach can clear some blockages but should be used as a last resort, since repeated use can damage older pipework over time. Always ventilate the room and never mix bleach with other chemical cleaners.
Why does my drain keep blocking in the same spot?
A drain that blocks repeatedly in the same place often points to a structural issue, such as a partial pipe collapse, tree root intrusion, or an incorrect pipe gradient, which usually needs a professional CCTV drain survey to diagnose properly.
Always wear protective gloves and eye protection when using chemical drain products, and never mix different chemical cleaners together, since some combinations release harmful fumes.
About the Author
Spire Homes Editorial Team researches and writes practical, UK focused home improvement guides covering renovation planning, financing, interior design, and property maintenance. Our content is reviewed for accuracy and updated as guidance changes.
