Bath not draining — how to clear the blockage
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Most likely cause & what to check
A bath that does not drain is usually blocked with hair and soap in the trap or the first section of waste pipe. Bath waste pipes are typically 40mm diameter and trap and chain waste configurations are common.
Remove the bath overflow cover plate (usually held by one screw) — hair can collect at the overflow grille on older baths with combined overflow/waste systems.
Remove the waste plug (or chain-and-plug) and use a bent wire or drain pull to extract hair from the waste opening. Even on baths without a visible hair build-up, a surprisingly dense plug of hair is often lurking 30–50mm inside the waste.
If this does not clear it, try plunging: block the overflow with a damp cloth, fill the bath slightly with water, and plunge over the waste outlet firmly 10–12 times. The combination of pressure and pulling action can shift a blockage further down the pipe.
If plunging fails, access the trap under the bath (via a panel at the end of the bath — the bath panel usually clips off). Unscrew or unclip the trap and clean it out. Baths often have a simple P-trap or running trap that is easily cleared.
If the blockage is beyond the trap, use a flexible drain snake (insert via the trap access, not through the waste outlet). Twist and push to break up the blockage, then flush with hot water.
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Frequently asked questions
What causes a bath to drain slowly?
The most common causes are hair and soap scum accumulating in the bath waste trap (U-bend), a pop-up waste mechanism that has not opened fully, or a partial blockage further downstream in the waste pipe. Hair blockages are typically within 100–200mm of the drain opening and are easy to remove by hand or with a drain snake.
Can I use a plunger on a bath?
Yes — cover the overflow hole with a wet cloth first (to stop air escaping and maintain suction), then use a standard flat or ball plunger over the drain. Push down slowly and pull sharply upward — repeat 10–15 times. This is effective for partial blockages close to the drain.
Is a slow-draining bath ever a sign of a serious drainage problem?
Occasionally — if the bath, toilet, and other drains all drain slowly simultaneously, the blockage is in the shared soil stack or outside drain rather than in the individual waste pipes. Check your outdoor inspection chamber; if it is full, the blockage is downstream and may require a drain company with rods or a CCTV camera.