Find where a shower leak is coming from

Track down exactly where a shower leak is coming from, from simple sealant checks to safely opening the wall.

SL-01Get set up and find your stopcockFind your stopcock, usually under the kitchen sink, and check it turns freely before you start. If you need to disturb pipework or open a wall later, you can shut the water off straight away. Get a torch, mirror, screwdriver, bucket, cloth and some food dye or washing-up liquid ready.

1 each · Torch

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1 each · Inspection mirror

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1 each · Bucket

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1 bottle · Food dye or washing-up liquid

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SL-02Check the shower dry firstWith the shower off, run your hand along every sealant line, grout joint, the door track or curtain rail, and the tray edge. Look for cracked, gappy or mouldy silicone, loose tiles, and any dampness already there from an old leak. Photograph anything odd so you know where to check first once the water is running.

SL-03Run the shower and watch while it's flowingTurn the shower on and let it run for a few minutes. Watch the tray edges, door seals, mixer valve and waste while water is actually hitting them, not just after you turn it off. Many leaks only show while water is flowing under pressure.

SL-04Check the pipework from below or behindFind the access point, usually a panel in the bath side, an airing cupboard, or a ceiling hatch in the room below. Wipe the trap, waste pipe and any joints completely dry, then have someone run the shower again while you watch. A drip here points to the plumbing, not the tray or tiles.

1 roll · Cloth or paper towel

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SL-05Do a bucket test to isolate the tray or wasteBlock the waste with a rag or an upturned bucket, then pour a bucket of water into the tray without running the shower itself. Watch for leaks appearing at floor level or from below. This tells you whether water is escaping through the tray or waste seal, rather than through the walls or door.

SL-06Check the door, hose and mixer connectionsWith the shower running, flex the hose and check both end fittings; a loose olive or a perished hose often only leaks under pressure. Check the door closes flush or the curtain fully overlaps the tray, since gaps here let water splash behind rather than run down the drain.

SL-07Work out what's behind the wall before you cut anythingIf you still haven't found it, you may need to open a small section of wall near the tray. Knock the tiles: a dull, dead sound usually means solid brick or block, a hollow, drum-like sound means plasterboard on a stud wall. Use a stud detector or magnet to trace a line of screw heads, drill a small 3mm test hole in a hidden spot, and check the dust: timber dust means a timber stud, fine grey swarf means a metal stud. If the board sits straight onto masonry with no deep cavity, it's dot-and-dab. In houses built before about 1930, a hollow sound with a crumbly, powdery hole usually means lath and plaster.

1 each · Stud detector

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1 each · Drill with 3mm bit

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SL-08Isolate power and water before you cut inCables and pipes can run almost anywhere in a wall, not just in the usual safe zones, and a metal stud frame will confuse a cheap detector even more. Use a cable and pipe detector, but still treat the whole area as live until you've proved otherwise. Turn the water off at the stopcock before cutting anywhere near a pipe run, and if there's any doubt about cables nearby, isolate the relevant circuit at the consumer unit first.

1 each · Cable and pipe detector

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SL-09Cut a small inspection holeOn a stud wall, cut a 100mm x 100mm hole with a plasterboard saw, keeping the cut away from any stud edge or fixing line you found earlier. On solid masonry, drill a ring of holes and chip out gently with a bolster chisel and hammer, wearing eye protection. On dot-and-dab or lath and plaster, work slowly, as both crumble more easily and lath and plaster can bring down a wider area than expected. Check the pipe joints, tray outlet and waste trap behind while the shower runs again.

1 each · Plasterboard saw

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1 each · Bolster chisel

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1 each · Safety glasses

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1 each · Dust sheet

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SL-10Refix any panel or patch you removedUse the right fixing for the wall behind the hole. Into a timber stud, use a wood screw into the centre of the stud. Into a metal stud, use a self-drilling metal-stud screw or a toggle-type hollow-wall fixing, never a wood screw or plain plastic plug, as these strip straight through 0.5mm steel. Into dot-and-dab, use a fixing long enough to reach the masonry behind the adhesive dabs, typically 60-75mm. Into solid masonry, drill to the plug's stated depth and use a matching plug and screw size.

1 pack · Wood screws (assorted)

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1 pack · Metal-stud self-drilling screws

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1 pack · Hollow-wall toggle fixings

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1 pack · Rawlplugs (wall plugs)

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SL-11Fix or reseal what you foundIf the cause is simple, such as failed silicone, loose grout or a worn hose washer, deal with it now while everything is dry and accessible. Rake out old silicone or grout fully before applying new, and let silicone cure for the time stated on the tube before running the shower again.

1 tube · Sanitary silicone sealant

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1 tub · Tile grout

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1 each · Sealant gun

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SL-12Dry out, tidy up and decide next stepsClean up any rubble or dust, and dry the affected area thoroughly with towels or a fan; leave it open to air for a day or two if you've cut into the wall. If the leak turned out to be a pipe joint, a damaged tray, or anything behind the waterproofing rather than a surface seal, get a plumber to fix it properly rather than closing the wall back up over it.

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