A blocked drain is one of those household problems that always seems to happen at the worst possible time. The good news is that most blockages can be cleared with basic tools and a bit of persistence — no plumber required. The key is identifying where the blockage is and choosing the right method to shift it.
Identifying the Blockage Location
Before you start, work out where the blockage actually is. This determines which method to use:
- Single fixture backing up (one sink, one shower) — the blockage is in the trap or waste pipe immediately below that fixture
- Multiple fixtures backing up — the blockage is further down the system, likely in a shared waste pipe or the main soil pipe
- Outside drain overflowing — the blockage is in the underground drainage between the house and the public sewer
- Manhole cover lifting or wet — the blockage is in or beyond the manhole chamber
Method 1: Boiling Water (Kitchen Sinks)
For kitchen sinks that are draining slowly (fat and grease build-up), this is always worth trying first:
- Boil a full kettle
- Pour it directly down the drain in a slow, steady stream
- Wait 5 minutes, then run the hot tap
- Repeat 2–3 times if needed
This works because fat and grease solidify in the pipes as they cool. Boiling water re-melts them. It won’t work on solid blockages or hair clogs, but it’s free and takes two minutes.
Method 2: Baking Soda and Vinegar
A mild chemical reaction that can shift moderate organic blockages:
- Pour half a cup of bicarbonate of soda down the drain
- Follow with half a cup of white vinegar
- Cover the drain opening immediately (the reaction fizzes — you want the pressure going down, not up)
- Wait 30 minutes
- Flush with boiling water
This is more effective than boiling water alone, but still only works on partial blockages caused by organic build-up. The Citizens Advice drainage responsibility guide clarifies who’s responsible for different parts of your drainage system.
Method 3: Plunger
The most effective manual method for sink, bath, and shower blockages. Use a cup plunger (flat bottom) for sinks and a flange plunger (extended rubber lip) for toilets.
- Block any overflow holes with a wet cloth — this ensures the plunger creates suction through the waste pipe, not through the overflow
- Fill the sink/bath with enough water to cover the plunger cup
- Place the plunger firmly over the drain opening, ensuring a good seal
- Pump vigorously 15–20 times with sharp, forceful strokes
- Pull the plunger off sharply — the alternating pressure and suction usually dislodges the blockage
- Repeat if needed
Method 4: Drain Snake or Zip-It Tool
For hair clogs in shower and bath drains, a plastic drain snake (sometimes called a Zip-It tool) is remarkably effective. It’s a cheap, disposable plastic strip with backward-facing barbs:
- Remove the drain cover
- Push the snake down the drain as far as it’ll go
- Pull it back out slowly — the barbs grab hair and debris
- Dispose of the extracted gunk (it will be disgusting)
- Flush with hot water
These cost about £2–£3 and clear hair blockages faster than any chemical product. For deeper blockages, a coiled metal drain snake (auger) reaches further and can break through tougher obstructions.
Method 5: Chemical Drain Cleaners
Chemical cleaners like Mr Muscle or HG drain unblocker work on organic blockages (hair, grease, soap scum). However, they have significant drawbacks:
| Product Type | Works On | Drawbacks |
|---|---|---|
| Caustic (sodium hydroxide) | Grease, hair, food | Can damage old pipes, harmful to skin/eyes |
| Enzyme-based | Organic build-up (slow acting) | Doesn’t work on solid blockages, takes hours |
| Acid-based | Hair, soap scum | Can damage certain pipe materials, very corrosive |
Use chemical cleaners as a last resort before calling a professional, not as a first line of attack. Never mix different chemical drain cleaners — the reactions can produce toxic fumes. Always follow the product instructions exactly.
Method 6: Outside Drain Blockages (Drain Rods)
If your outside drain or manhole is backing up, you’ll need drain rods:
- Lift the manhole cover downstream from the blockage (the chamber that’s empty or has low water)
- Screw your drain rods together and feed them into the pipe in the direction of the blockage
- Push and twist clockwise only — anti-clockwise can unscrew the rod joints, leaving a rod stuck in the pipe
- When you feel resistance, work the rods back and forth to break through the blockage
- Once clear, flush with a hose to ensure the pipe is fully open
Family Handyman’s drain clearing guide provides additional techniques for stubborn outdoor blockages.
Preventing Blocked Drains
- Kitchen: Never pour cooking fat or oil down the sink. Wipe greasy pans with kitchen roll before washing
- Bathroom: Fit a hair catcher over shower and bath drains. Clean it after every shower
- Outside: Keep drain grates clear of leaves and debris. Consider fitting gutter guards to reduce material reaching ground-level drains
- Monthly maintenance: Pour boiling water down kitchen and bathroom drains once a month as preventative maintenance
When to Call a Plumber
Call a professional if:
- The blockage keeps returning despite clearing it
- Multiple drains are blocked simultaneously (suggests a main drain issue)
- You suspect tree root ingress — common with older clay drainage pipes
- There’s a bad smell from drains even when they’re flowing freely (possible broken pipe)
- Sewage is backing up into the house — this is an emergency
Most plumbers charge £80–£150 to clear a drain, or £200–£400 if a CCTV drain survey is needed to diagnose the problem. For anything beyond the boundary of your property, contact your water company — public sewer blockages are their responsibility at no cost to you.
