Leaking Shower: Signs, Causes and How It Gets Fixed

A leaking shower is almost always one of three things: a shower rose or mixer that drips, a pipe or fitting leaking inside the wall, or waterproofing and grout that have let go. Each one leaves a different sign, and each one gets fixed a different way.

The expensive mistake is guessing. Pulling tiles off to chase a leak that turns out to be in the wall behind them, or re-grouting a shower that actually has a split pipe, costs you twice. Here’s how to tell them apart, and how a plumber confirms which it is before anything gets opened up.

The three kinds of shower leak

Before you do anything, it helps to know what you’re looking at.

Type	Where the water goes	The tell-tale sign
Dripping rose or mixer	Down the drain, where you can see it	Water dripping from the head or spout after the tap is off
Leaking pipe or fitting in the wall	Into the wall cavity, all day and night	The water meter moves with every tap off
Failed waterproofing or grout	Under the tiles and out the sides, only when the shower is used	Damp that gets worse after showers and dries out between them

That last column is the whole diagnosis in miniature. The rest of this post fills it in.

A dripping shower rose or mixer

This is the easy one, and the cheapest. If water keeps dripping from the shower head or the spout after you’ve turned it off, a washer, a cartridge or a ceramic disc in the tap or mixer has worn out.

It wastes water and it’s annoying, but it isn’t damaging your house, because every drop goes where it’s supposed to: down the drain. Our dripping tap help page walks through what you can check and what the repair involves.

The only time a drip matters structurally is when the mixer body itself is leaking behind the wall plate. Then it behaves like the next category.

A leaking pipe or fitting inside the wall

Behind every shower wall there are hot and cold supply pipes running to the mixer, and a pipe up to the rose. Joints can fail, older copper can pinhole, and a mixer body can crack. Because these pipes are under mains pressure all the time, a leak here runs whether anyone is showering or not.

The signs:

• A damp patch or bubbling paint on the other side of the wall, often in the next room or a hallway
• Skirting boards that have swollen, split or come away from the wall
• Mould at the base of the wall, or a musty smell that doesn’t go away
• Floor coverings lifting next to the bathroom
• A water bill that has jumped for no reason you can think of

Why is water coming through the wall next to my shower?

If the wall beside or behind the shower is wet and it stays wet even when nobody has showered for a day or two, suspect a supply pipe. Water under pressure finds its way along the frame and shows up wherever the plasterboard or timber gives it an outlet, which is often a metre or more from the actual leak.

The meter test settles it. Turn off every tap, the dishwasher, the washing machine and any irrigation, then read your water meter and check it again after 15 to 30 minutes without using any water. If it has moved, you’re losing water on your side of the meter. Our guide to finding your water meter shows where to look if you’ve never gone hunting for it.

Failed waterproofing or grout

Under the tiles in a shower recess there should be a waterproof membrane that turns the whole recess into a tray draining to the waste. Grout and silicone are not waterproof on their own. They slow water down, and the membrane underneath does the real work.

When the membrane fails, or was never done properly in the first place, water that gets through cracked grout or perished silicone soaks into the bed under the tiles and travels sideways. It’s a common story in bathrooms from the 1970s and 80s around Castle Hill, Baulkham Hills and Carlingford, and in some newer estate builds where the membrane was rushed at the corners.

The signs:

• Damp or staining that appears after showers and fades between them
• Grout that is cracked, crumbling, dark or permanently damp, especially along the bottom row and in the corners
• Tiles that sound hollow when you tap them, or have started to move
• Swollen door jambs or architraves at the bathroom door
• Damp showing on a ceiling below, if the bathroom is upstairs

This kind of leaking shower only leaks when water is being poured onto it, which is exactly why the meter test comes back clean.

Is it the waterproofing or the pipes?

Put the two tests together:

• Meter moves with everything off: it’s a pressurised pipe or fitting.
• Meter is still, and the damp follows shower use: it’s waterproofing, grout, silicone, or the seal around the floor waste.

A blocked or slow shower drain can make a marginal waterproofing problem much worse, because water sits against the grout for longer. If yours drains slowly, see how to clean a shower drain.

How to tell if your shower is leaking behind the tiles

You can narrow it down yourself before you call anyone:

1. Do the meter test above.
2. Don’t use the shower for two or three days and see whether the damp patch dries or stays.
3. Then run the shower with the water aimed only at the floor for ten minutes, and check the damp spot. Then aim it at the walls and check again.
4. Look closely at the grout and silicone in the corners and around the floor waste.

That tells you which category you’re in. It doesn’t tell you exactly where the water is getting out, and that’s what decides how much of the bathroom has to be disturbed.

How a plumber confirms it before lifting tiles

This is where leak detection earns its keep. Rather than opening up the wall to have a look, we isolate and test.

Supply pipes get pressure-tested on their own, hot and cold separately, so we know whether the leak is on the pipework and which side it’s on. A thermal camera picks up a hot water leak behind tiles by the heat it spreads through the wall. Moisture meters map how far the damp has travelled, and a flood test on the shower floor shows whether the membrane is holding.

The result is a spot on the wall or floor, and a clear answer on whether it’s a pipe or the waterproofing. One section gets opened up instead of the whole recess. If your first sign was a bill or a damp patch rather than anything in the shower itself, our hidden leak help page covers what to do in the meantime.

Can a leaking shower be fixed without removing tiles?

Sometimes. It depends on which kind of leak you have.

• A dripping mixer or rose: yes, almost always. It’s a repair from the front.
• A leaking pipe in the wall: usually only one or two tiles, or access from the other side of the wall if it’s a cupboard or a room we can patch. Located precisely, it’s a small hole.
• Cracked grout and failed silicone, with the membrane still intact: yes. Raking out and re-grouting, then re-sealing the corners and floor waste, can stop it.
• A failed membrane: honestly, no. Surface sealers applied over the grout can slow it down, but they don’t replace a membrane. A proper fix means the tiles come up, the membrane is redone, and the shower is re-tiled.

That last one is the job everyone wants to avoid, which is why finding out for certain first matters so much.

What you can safely do yourself, and what needs a plumber

Safe to do yourself:

• The meter test and the shower-use test above
• Replace perished silicone around the recess and at the floor waste
• Keep the shower drain clear
• Turn off the water at the meter if you find water actively spreading and can’t work out where from

Needs a licensed plumber:

• Anything behind the wall, including pipes, fittings and the mixer body
• Replacing tap cartridges and mixer internals, if you’re not confident with them
• Pressure testing and leak location
• Waterproofing and membrane work, which should be done by a qualified waterproofer to the relevant Australian Standard

Getting a leaking shower sorted

If you’ve got swollen skirting, a damp wall or a meter that won’t sit still, it’s worth finding out exactly what’s going on before anyone quotes you a new bathroom. We work across the Hills District, Hornsby Shire and the Upper North Shore, and we’ll tell you what we find and what it will take to fix, with a fixed price agreed before any work starts. See our water leak detection service for how we find leaks without opening things up.