Bathroom basin draining slowly — how to clear it
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Most likely cause & what to check
Bathroom basin slow drains are almost always caused by hair and soap scum caught on the pop-up waste plug mechanism or in the trap just below the basin.
Remove the basin plug or waste cover. If it is a pop-up waste (operated by a rod at the back of the tap), pull it out — there is usually a clip or hook on the underside where hair collects. Clean it thoroughly.
With the plug removed, insert a drain pull tool or a bent wire hook into the drain and pull out any accumulated hair. A surprising amount of hair collects even in just a few months of normal use.
If the basin still drains slowly after removing the visible blockage, the trap under the basin needs clearing. Place a small bucket under the U-trap, unscrew the trap (hand-tight or with a pair of grips with cloth to protect the plastic), empty it, and rinse clean.
For basins with bottle traps (a cylindrical trap common in modern bathrooms), unscrew the bottom section — they twist off anti-clockwise. Clean the internal bottle and tube.
Prevent future slow drains by rinsing a kettleful of hot water down the basin weekly, and fitting a drain cover that catches hair before it enters the waste.
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Frequently asked questions
Why does my bathroom basin fill up with water when I run the tap?
The waste pipe is partially or fully blocked — usually hair and soap scum in the trap or waste mechanism. The basin is filling faster than it drains. This is almost always fixable with the techniques in this guide, without needing a plumber.
My basin has a pop-up waste mechanism — how do I clear it?
Pop-up wastes accumulate hair and soap around the plug and the mechanism linkage below the basin. Lift or unscrew the pop-up plug head (most twist off or lift out with a pull). Reach down into the drain opening and remove any matted hair. Clean the linkage arm and pivot rod below the basin while you have access.
How often should basin drains be cleaned?
Every 2–4 weeks in households with long hair, monthly otherwise. Pouring 500ml of boiling water (or very hot water from the kettle) down the drain weekly helps dissolve soap scum before it builds up. Enzyme drain cleaners used monthly also break down organic matter without harsh chemicals.