How to Unblock a Drain: Sink, Shower and Bath
The quick answer: to unblock a sink, shower or bath, first pull out any hair or debris you can reach at the plughole, then try a plunger. If a shower, bath or basin still drains slowly, pour in a bathroom drain unblocker, leave it for 15 minutes (overnight for stubborn blockages), and flush with plenty of hot water. Greasy kitchen sinks need a different approach: clean the trap or use a drain snake. If several drains are blocked at once, or water backs up outside, call a plumber or your water company.
By the GLEAN team · Updated October 2026
Most household blockages are caught in the first metre of pipe: hair and soap scum in bathrooms, fat and food in kitchens. That's good news, because you can usually clear them yourself in under half an hour without taking anything apart. This guide covers what causes each type of blockage, the order to try things in, and when to stop and call someone.
What you'll need
- Rubber gloves (and eye protection if you're using a chemical unblocker)
- A cup plunger, plus a damp cloth to block the overflow
- A bucket and old towel (if you need to open the trap under the sink)
- A plastic drain snake or hair-removal tool for showers and baths
- GLEAN Drain Unblocker Liquid for shower, bath and basin blockages you can't reach
Why drains block: sink, shower and bath
| Drain | Usual cause | Early warning signs |
|---|---|---|
| Kitchen sink | Cooking fat, oil and food scraps that set hard in cold pipes | Slow draining, gurgling, a stale or greasy smell |
| Shower | Hair bound together with soap and shampoo residue | Water pooling round your feet, a ring of scum in the tray |
| Bath | Hair, soap scum and bath products, often caught in the plug mechanism | Bath takes ages to empty, bubbles rising from the plughole |
| Bathroom basin | Hair, toothpaste, soap and shaving residue | Slow draining, smell from the overflow |
Blockages are more common in winter. Pipes are colder, so fat sets faster, and the Christmas fortnight puts more grease down kitchen sinks than any other time of year.
How to unblock a drain, step by step
Work through these in order and stop as soon as the water runs freely.
1. Clear the plughole
Put your gloves on. Remove the plug, pop-up stopper or shower drain cover (most twist or lift off). Pull out any visible hair and gunk, then use a plastic drain snake to hook out what's just below the surface. In showers and baths this alone fixes a surprising number of "blocked" drains.
2. Use a plunger
Run enough water to cover the plunger cup. Hold a damp cloth firmly over the overflow hole (otherwise the pressure escapes through it), seal the plunger over the plughole and pump firmly 10 to 15 times, then pull away sharply. Repeat two or three times. If the water starts to drop, run the hot tap for a minute to carry the loosened debris away.
Don't plunge if you've already put a chemical unblocker down the drain: flush it through with water first so nothing splashes back at you.
3. Showers, baths and basins: use a bathroom drain unblocker
If a bathroom blockage is further down the pipe than you can reach, a liquid unblocker is the next step. GLEAN Drain Unblocker Liquid is a concentrated, lab-tested formula that goes straight to the blockage and dissolves hair, sludge and soap scum, clearing stubborn blockages in one treatment. It gets to work almost instantly, works on slow-draining water and full blockages, and is safe for all pipes and septic systems. It's made for bathroom drains: for a greasy kitchen sink, skip to step 4.
- Bail out standing water if you can, so the liquid reaches the blockage rather than being diluted.
- Shake the bottle well.
- Pour slowly down the drain: the whole 500ml bottle, or half of the 1 litre bottle.
- Leave it for about 15 minutes, or overnight for tough blockages.
- Flush with plenty of hot water.
- Repeat if needed. If water still won't drain after a second treatment, try a drain snake (step 5) or call a plumber.
Safety: always read the label and follow the instructions. This is a chlorine-based product: never mix it with other cleaners, especially toilet cleaners or anything acidic, because that can release dangerous chlorine gas. Wear gloves and eye protection, keep the room ventilated, and don't use one drain product straight after another. Take care on chrome, gold-plated fittings and worn enamel, and don't use it on aluminium. Keep it out of reach of children and pets.
4. Kitchen sinks and basins: clean the trap
This is the main fix for kitchen sinks, where fat and food scraps collect in the U-shaped trap under the sink. Put a bucket and towel underneath, unscrew the two plastic nuts by hand, and empty the trap into the bucket. Rinse it out, check the washers are seated properly, and screw it back hand-tight. Run the tap and check for drips. Don't do this straight after using a chemical unblocker: flush the drain with water first.
5. Use a drain snake further down
For a blockage beyond the trap, feed a longer drain snake (auger) into the pipe, turning it as you go until you feel resistance. Twist to break up or hook the blockage, then pull back slowly and flush with hot water.
Kitchen sink full of grease? What works and what doesn't
Fat is the main culprit in kitchen sinks. It goes down as a liquid, cools, and sticks to the pipe walls, catching food scraps until water can barely get through. Bathroom unblockers like ours are formulated for hair and soap, not fat, so for a kitchen sink rely on the trap (step 4) and a drain snake (step 5).
- Do: wipe greasy pans with kitchen roll before washing, pour cooled fat into a container for the bin, and use a sink strainer.
- Do: run hot tap water for a minute after washing up to keep fat moving.
- Don't: pour boiling water from the kettle down the sink. It can soften plastic pipe joints and crack some sinks, and once it cools the fat sets again further down.
- Bicarbonate of soda and vinegar: fine for freshening a smelly drain, but it fizzes rather than dissolving fat or hair, so it rarely shifts a real blockage.
Shower and bath drains: stopping hair blockages
Hair doesn't break down on its own. Once a few strands catch on the drain cover or plug mechanism, soap scum binds them into a mat that gets thicker every shower.
- Fit a hair catcher over the shower drain and empty it after every few showers.
- Lift and clean the shower drain cover once a week.
- For baths with a pop-up plug, unscrew the plug every month or two and clear the hair wrapped around the stem.
- Regular use of drain unblocker helps stop slow-running pipes turning into a blockage. Follow the label directions for maintenance doses.
When to call a plumber or your water company
Stop and get help if:
- More than one drain is blocked at once (for example the sink and the shower, or the toilet gurgles when the bath empties). That points to a blockage in the main drain, not the individual pipe.
- Water or sewage is coming up from an outside drain or gully.
- There's a persistent sewage smell indoors.
- The blockage keeps coming back within days of clearing it, which can mean a damaged or sagging pipe.
In England and Wales, the pipes inside your property boundary that serve only your home are usually your responsibility. Shared drains and sewers are usually the responsibility of your water company, so if neighbours are affected too, call them first.
How to stop drains blocking again
- Never pour fat, oil or coffee grounds down the sink.
- Use a sink strainer in the kitchen and a hair catcher in the shower.
- Run hot tap water for a minute after washing up.
- Clean plugholes and drain covers weekly in busy bathrooms.
- Treat slow drains early, before they block completely.
Slow bathroom drains often go hand in hand with damp and condensation. If you're giving the bathroom a winter refresh, see our guide to removing black mould from bathroom walls.
Frequently asked questions
How long does drain unblocker take to work?
GLEAN Drain Unblocker Liquid starts working straight away and is designed to clear a blockage in about 15 minutes. For stubborn clogs, leave it overnight, then flush with plenty of hot water. If the drain is still blocked after a second treatment, it's time to use a drain snake or call a plumber.
Can I use drain unblocker on a completely blocked drain?
Yes, for showers, baths and basins: GLEAN Drain Unblocker Liquid works on full blockages as well as slow-draining water. Remove as much standing water as you can first so the liquid reaches the blockage instead of sitting on top of the water. Pour it in slowly and give it time to work, overnight if needed.
Is drain unblocker safe for septic tanks?
Some are and some aren't, so check the label. GLEAN Drain Unblocker Liquid is suitable for all pipes and septic systems when used as directed.
Can I use a plunger after drain unblocker?
Not straight away. Plunging can splash the product back out of the plughole. Flush the drain with plenty of water first, then plunge if you need to.
Why does my drain smell even though it isn't blocked?
Smells usually come from a build-up of fat, soap scum or hair just below the plughole, or from a dry trap in a sink or shower you rarely use. Clean the plughole and drain cover and run the tap for a minute to refill the trap. In a bathroom, a dose of drain unblocker clears the sludge that causes it; in a kitchen, clean the trap.
Is boiling water good for unblocking drains?
It's best avoided. Boiling water can soften plastic pipe joints and damage some sinks and toilet bowls, and it only moves fat a short way before it sets again. Use hot tap water instead.