How to unblock a bath that drains slowly or not at all

Why baths block, and why it is usually close to the plug

A bath waste is a narrow pipe, usually 40mm, running a short distance from the plug hole to a trap under the bath and then out through the wall or floor. Long hair wraps around the plug mechanism and the crossbar under the grille, soap scum binds it into a mat, and each bath adds a little more. By the time the water is draining slowly, there is often a plug of hair a few centimetres below the grate.

Because the trap under a bath has to fit in the small gap between the bath and the floor, it is often a shallow design with tight bends. That makes it easy to block and awkward to reach, which is why working from the plug hole first saves a lot of effort.

What you need

You can clear most bath blockages with a few inexpensive tools. A flat-bottomed cup plunger seals better on a bath than a flanged toilet plunger.

• Rubber gloves and an old towel
• A plastic drain snake or hair-removal strip with barbs
• A cup plunger
• A wet cloth to seal the overflow
• A screwdriver for the plug grate and bath panel
• A bowl or shallow tray that fits under the trap

Step 1: take out the plug and clear the hair

Bail out standing water with a jug so you can see the plug. A plug on a chain lifts straight out. A click-clack or pop-up plug usually unscrews anticlockwise from its stem; some pull straight up. Clean the hair and slime off the underside of the plug and its stem, and check whether the grate below has a screw in the middle. If it does, removing it gives you much better access.

Push a plastic drain snake down the plug hole, twist it and pull it out slowly. Repeat until it comes out clean. This one step clears a large share of slow-draining baths, and the snake costs very little. Run the taps for a minute to check the water now drains freely.

Step 2: plunge with the overflow sealed

Plunging only works if the pressure has nowhere else to escape. The overflow near the top of the bath is connected to the same waste, so press a wet cloth firmly over it, or ask someone to hold it there. Leave enough water in the bath to cover the plunger cup.

Seat the plunger over the plug hole and pump it sharply ten to fifteen times without breaking the seal, then lift off and watch the water. Repeat two or three times. If the water starts to drop, run hot water from the tap for a couple of minutes with a squirt of washing-up liquid to carry the loosened soap away.

For more on choosing a plunger and getting a good seal, see our guide on how to use a plunger.

Do not pour a kettle of boiling water into an acrylic bath or down a plastic bath waste. Very hot water can soften acrylic and plastic joints. Hot water from the tap is enough.

Step 3: clean the trap under the bath

If plunging does not work, the blockage is probably in the trap. Remove the bath panel: most side panels are held by screws under caps along the top or bottom edge, or clip into a plinth and pull away from the bottom. Take care with older panels, which can crack.

Put a tray and towels under the trap, then unscrew its plastic nuts by hand. Empty and rinse it, clear the pipe either side as far as you can reach, and check the rubber washers are seated properly before refitting. Tighten by hand, run a full bath's worth of water through it, and watch every joint for drips before putting the panel back.

If you find water already on the floor under the bath, or the overflow or waste joints look damp, the blockage may not be your only problem. Our guide to a leaking bath explains how to trace where the water is escaping, and replacing bath waste and overflow fittings covers what is involved when the fittings themselves have failed.

Chemical drain unblockers and baths

Chemical unblockers can shift soap and hair, but check the label says the product is safe for your bath material and plastic pipework before using it. Never pour one into a bath full of standing water, because you cannot then plunge or dismantle the trap safely, and never mix two products. If you have already used one and the bath is still blocked, tell the plumber what you used before they start work.

Biological and enzyme cleaners are gentler and help with smells and slow drainage over time, but they are too slow to clear a bath that will not drain at all.

When it is not the bath at all

If the bath is only the first fitting to show the problem, clearing its trap will not help. Warning signs are gurgling when other fittings drain, bath water rising in the shower tray, a smell from the plug hole, or an overflowing gully outside. In a flat, a slow bath can also mean the shared soil stack is partly blocked, which is usually for the freeholder or managing agent to deal with.

A bath that blocks again within weeks points to something in the pipe itself: a poor fall on a long waste run, a sag where the pipe crosses a joist, or a build-up further along. Our guide on why drains keep blocking covers the usual causes. The same basic method also works on basins, and how to unblock a sink explains the differences.

Stop the bath blocking again

Fit a hair catcher over the plug hole and empty it after each bath. Brush long hair before bathing rather than in the bath. Pull out the click-clack plug every few weeks and clean the stem. Keep bath oils and thick bath products to a minimum, as they coat the inside of the pipe and trap hair.

Call a plumber for a bath that will not clear

Loyal Plumbers clears blocked baths, wastes and drains across London and everywhere inside the M25, with 10 vans working 24 hours a day. If the bath still will not drain after cleaning the trap, other fittings are affected, or water is coming up somewhere else, call 020 4652 8585 or send an enquiry.

Tell us whether the bath panel comes off, whether you have used a chemical unblocker, and whether the basin, shower or toilet are also slow. Our call-out charge is £60, and the engineer explains what clearing the blockage involves before starting.