How to unblock a shower drain — hair, scum and the stuff underneath

Run the shower for thirty seconds and watch. Water that drains but slowly means a partial restriction in the shower's own waste run — almost always hair. Water that sits still and doesn't move at all usually means the trap is completely plugged, or the blockage is further down the branch pipe.

Now flush the toilet and run the basin in the same bathroom. If those back up or gurgle too, the shower isn't the problem — the soil stack or the underground drain is, and nothing you do at the shower tray will fix it.

Most shower grilles either unscrew with a small cross-head or lever up with a flat blade. Underneath you'll find the trap: a shallow cup with a removable insert on modern trays, or a fixed bottle trap on older ones.

Pull the insert out and empty it. Wear gloves — the smell is bacterial biofilm, not sewage, but it's unpleasant. Scrub the insert and the visible rim of the trap with an old toothbrush.

A Zip-It strip or a flexible drain brush costs a couple of pounds and is the single most effective tool for a shower. Push it in, twist a half-turn so the barbs bite the hair mass, and pull straight out. Repeat until it comes back clean — usually three or four passes.

Don't force a wire coat hanger down. Modern shower waste runs are thin-wall plastic and a sharp wire end will score or puncture them, which turns a ten-minute job into a floor-up repair.

Boil a kettle, let it stand for a minute so it's hot rather than boiling (boiling water can distort plastic traps and crack resin trays), tip in a large mug of soda crystals, then pour the water through slowly.

Soda crystals dissolve the fatty soap scum binding the hair together. Leave it fifteen minutes and flush with hot water. Avoid caustic drain unblocker in a shower — it sits in the trap, does very little to hair, and makes the drain dangerous for anyone who has to open it afterwards.

A small cup plunger over the shower waste will shift a loosened plug. Cover any overflow or second waste in the same tray with a wet cloth first, otherwise the pressure escapes and the plunger does nothing.

Short, sharp strokes with a good seal beat long slow ones. Ten strokes, then run water and check.

If the shower is still slow after all that, the restriction is in the horizontal branch pipe. On a ground-floor shower this often runs to an external gully — go outside and look at the gully while someone runs the shower. Water backing up at the gully means the blockage is external, not internal.

A hand snake fed through the waste will reach a couple of metres. Beyond that you need a mini-jetter, which is where a professional comes in.

Multiple slow fixtures, gurgling toilets, smells from the gully or water rising in the shower tray when you flush the toilet all point to the underground drain. That is a jetting job, not a DIY one.

It's also worth knowing whether that underground run is even yours. Since the 2011 private sewer transfer, most shared drains and everything past your boundary belong to the water company, who clear them free. Our free drain responsibility checker settles it in about thirty seconds.

DrainFixer is a small family-run firm covering East Grinstead and 20 miles around, 24 hours a day. Jetters and CCTV cameras on every van, and an honest answer about whose drain it is.

Call 0330 1331 347 and you'll speak to a person.