How to Fix a Leaking Shower

Start by finding the source

A leaking shower is a symptom, not a diagnosis. Water can escape through the tapware, around the screen, through grout and silicone, past a failed membrane or around the floor waste, and the damage it causes often shows up somewhere else entirely: a swollen door frame in the hallway, a mouldy skirting board in the next room, or a stain on the ceiling below an upstairs bathroom.

Patching the wrong thing is the most common and most expensive mistake. Re-siliconing a shower that is actually leaking from a cracked pipe fitting inside the wall does nothing except hide the evidence for a few more weeks. So before buying anything, spend a few days narrowing it down.

Signs that a shower is leaking

• Floor tiles that sound hollow or drummy when tapped with a coin, or tiles that have started to lift near the shower
• Grout that stays dark long after everything else in the room has dried
• Cracked or mouldy silicone where the walls meet the floor or the screen meets the tiles
• Swollen skirting boards, architraves or door frames just outside the bathroom
• Damp, bubbling or peeling paint on the other side of the shower wall
• Stains or sagging plaster on a ceiling below
• A musty smell that does not go away with ventilation
• Water on the floor outside the shower after every use

Test each possible source one at a time

The simplest diagnostic method costs nothing. Wet one part of the shower at a time, leave it for a day or so, and watch for fresh damp. Mark the edge of any existing stain with a pencil so you can see if it grows.

1. The mixer and pipework. Turn the shower on without standing in it, and aim the head away from the walls, into a bucket if you can. If damp appears behind the shower wall only when the tap is running, or even when nothing has been used, the problem may be the mixer body or a pipe connection inside the wall. A further check is the water meter: turn off every tap in the house, read the meter, and read it again an hour or two later. If it has moved, water is escaping somewhere under pressure.

2. The screen and its seals. Spray water directly at the screen door, its hinges and the bottom seal for a few minutes, without wetting the floor tiles more than necessary. Water on the bathroom floor or damp outside the room afterwards points to perished wipers, a door that has dropped out of alignment, or gaps in the silicone where the screen frame meets the tiles.

3. Grout and silicone joints. Wet the tiled walls, particularly the internal corners and the wall-floor junction, with a hand-held spray or a jug. Cracked grout lines and silicone that has pulled away from the tile are common entry points. Grout is not waterproof; it relies on the membrane behind it.

4. The floor and membrane. If the floor tiles are drummy, the grout on the floor stays dark, and damp shows outside the room even when the walls and screen have tested dry, the waterproofing membrane under the tiles may have failed, or there may never have been one. This is common in bathrooms built before membranes became standard practice.

5. The floor waste. Pour a steady stream of water straight into the waste with a jug or hose, without wetting the surrounding tiles. If damp appears below or beside the shower, the seal between the waste and the membrane (often called the puddle flange) may be leaking, or the waste pipe itself may be cracked or poorly connected.

A moisture meter makes all of this more reliable, because it shows damp in plaster and timber before you can see it. They are inexpensive to buy or hire, and many leak detection specialists and plumbers carry them. Where the source still is not obvious, a specialist leak detection service using thermal imaging or pressure testing can save opening up the wrong wall.

What a homeowner can reasonably fix

Screen seals and wipers. Replacement wipers and door seals are usually a push-on fit, and matching the profile of the old one is the main challenge. Adjusting a dropped door so it closes squarely against its seal is often a simple hinge adjustment.

Silicone at the screen and corners. Old silicone has to be removed completely, the joint cleaned and dried thoroughly, and new mould-resistant sanitary silicone applied in a continuous bead. Silicone laid over old silicone or over a damp joint will not bond properly. Allow the full cure time on the product before the shower is used.

Minor grout repairs. A few cracked grout lines on a wall can be raked out and refilled. Where the grout is failing across a whole shower, regrouting is a bigger job, and it only helps if the membrane behind is sound.

Sealing. A penetrating grout and tile sealer can reduce water absorption through grout. It is a maintenance measure, not a repair for a failed membrane, and it will not stop a leak coming from pipework or the waste.

When it needs a licensed tradesperson

In NSW, work on water supply pipes, tapware connections and drainage is plumbing work that generally has to be done by a licensed plumber. That includes replacing a mixer body inside the wall, repairing a leaking pipe connection, and replacing or resealing a floor waste. If you are unsure whether a job needs a licence, NSW Fair Trading can confirm.

A failed or missing membrane cannot be fixed from the surface. The lasting repair is removing the tiles, repairing whatever the water has damaged underneath, and installing a new membrane before retiling. Waterproofing work in NSW is licensed work, and it should be done to the relevant Australian Standard for wet areas. Your waterproofer should be able to explain how their work complies.

Call someone promptly if you see:

• Soft or springy floor near the shower, which can mean water has reached timber joists or sheeting
• A stain spreading on a ceiling below the bathroom
• The water meter moving with every tap turned off
• Mould or damp appearing in a neighbouring room, or in the unit below if you live in a strata building

In a strata building, let the owners corporation or managing agent know early if water may be reaching common property or another unit. It is also worth checking your home insurance policy, as cover for gradual leaks and the damage they cause varies between policies.

Repair or renovate?

A leak from a seal, a silicone joint or a tap is a repair. A leak from a failed membrane in an older bathroom is often the point where renovating makes more sense than patching, because the tiles have to come off anyway and the pipework, linings and floor underneath are usually due for attention too. A good tradesperson will tell you which situation you are in rather than selling you the bigger job.

If you are in Hornsby Shire and the tests point to the membrane, we can look at the room and quote the fix or the full renovation.

Related pages

• Bathroom waterproofing — how a membrane, falls and upstands are done properly
• Complete bathroom renovations — when the whole room is due
• Bathroom renovation cost guide — rough bands and the factors that move a price