How to Unblock a Drain
From simple sink blockages to stubborn outside drains - fix it fast without calling a plumber.
Difficulty
Easy
Time
30 - 60 mins
Cost
£5 - £30
Before You Start
Never mix different chemical drain cleaners - they can react and produce toxic fumes. Wear rubber gloves and eye protection when using chemicals. If you have a septic tank, avoid chemical cleaners entirely as they kill the bacteria that break down waste. For outdoor drains, be aware that raw sewage is a biohazard - wear gloves and wash hands thoroughly.
A blocked drain is one of the most common household problems and usually one of the easiest to fix yourself. The cause is almost always a buildup of hair, soap scum, grease or food. The key is to start with the simplest method and escalate if it does not work. Most blockages clear with a plunger alone. Chemical cleaners should be a last resort because they can damage older pipes.
What You Will Need
Tools
- - Plunger (cup style for sinks, flange style for toilets)
- - Drain snake or auger
- - Bucket and old towels
- - Rubber gloves
- - Wire coat hanger (straightened, for hair clogs)
Materials
- - Bicarbonate of soda
- - White vinegar
- - Boiling water
- - Chemical drain cleaner (last resort)
Step-by-Step Instructions
Try Boiling Water First
Boil a full kettle and pour it slowly down the drain in two or three stages, waiting a few seconds between each pour. This dissolves soap and grease buildup. For sinks with standing water, bail out most of the water first. Do not use boiling water on PVC pipes if the water will sit in the pipe - the heat can soften the joints.
Use the Baking Soda and Vinegar Method
Pour half a cup of bicarbonate of soda down the drain, followed by half a cup of white vinegar. Cover the drain with a wet cloth and leave for 30 minutes. The fizzing action breaks up organic buildup. Flush with boiling water.
Try a Plunger
Fill the sink or bath with enough water to cover the plunger cup. Block the overflow hole with a wet cloth (this is essential - without it, the plunger has no suction). Place the plunger over the drain and pump vigorously 15-20 times. Pull away sharply on the last pump to break the seal.
Use a Drain Snake
If the plunger fails, feed a drain snake into the plughole. Push and twist as you go. When you feel resistance, you have reached the blockage. Twist and push to break it up or hook it out. Flush with hot water.
Clear the Trap
For kitchen sinks, place a bucket under the U-bend (trap) and unscrew it. Clear any debris by hand. This is usually where the blockage sits. Refit hand-tight.
For Outside Drains
Remove the drain cover. If there is standing water, the blockage is downstream. Use drain rods (available to hire from tool hire shops) - push and twist in a clockwise direction only (anticlockwise unscrews the rods and you lose them in the drain). Flush with a hose.
Pro Tip: Prevent Future Blockages
Fit a hair catcher over bath and shower drains. Never pour cooking oil or fat down the sink - wipe greasy pans with kitchen roll before washing. Run hot water for 30 seconds after washing up to flush grease through.
Pro Tip: The Wet Cloth Trick
When using a plunger on a sink, always block the overflow hole with a wet cloth held firmly in place. Without this, air escapes through the overflow and the plunger cannot create proper suction.
Common Mistakes to Avoid
- - Not blocking the overflow when plunging - the suction escapes and the plunger does nothing
- - Turning drain rods anticlockwise - the rods unscrew from each other and get stuck in the drain
- - Using chemical cleaners repeatedly - they corrode older metal pipes and damage plastic joints
- - Ignoring slow drains - a slow drain is a blocked drain in progress, fix it early
- - Pouring boiling water into a toilet bowl - thermal shock can crack the ceramic
When to Call a Professional
If the blockage is in the main sewer line (multiple drains backing up simultaneously), if you smell sewage in the house, or if drain rods cannot clear the blockage, call a drainage specialist. They have CCTV cameras and high-pressure jetting equipment. Most drainage companies charge around 80-150 pounds for a standard callout.