You have noticed water staining on the ceiling below your bathroom. Or perhaps the paint on the wall outside the shower has started bubbling. Maybe the carpet in the adjoining room feels damp in the mornings. Your first instinct is to call a plumber. But here is the thing: the problem might not be your pipes at all. It might be your grout.
At Mr Grout, we have spent over 27 years fixing showers that homeowners were told needed to be ripped out and replumbed. In most cases, the leak was coming straight through deteriorated grout. Not the plumbing. Not the waterproofing. Just the grout. Knowing the difference can save you thousands.
Here are the seven clearest signs your shower is leaking through the grout, and what to do about each one.
1. Water Stains on the Ceiling Below the Bathroom
This is the sign that sends most people straight to a plumber. A brown or yellowish ring spreading across the ceiling directly under your upstairs bathroom. It is alarming, and it should be. But do not assume it is a burst pipe. If the stain appears gradually rather than suddenly, and if it worsens after someone showers, the water is almost certainly travelling through failed grout joints and pooling beneath the tiles before soaking through the subfloor.
A plumber will check your pipes and find nothing wrong. A grout specialist will find the entry point in under ten minutes.
2. Loose or Drummy Tiles in the Shower
Tap on your shower floor tiles with a coin or the handle of a screwdriver. A solid tile returns a sharp click. A drummy tile sounds hollow. That hollow sound means the tile has de-bonded from the substrate, and the most common cause is water penetrating through the grout and breaking down the adhesive underneath.
Once tiles start moving, the problem accelerates. Every step you take on a loose tile pumps more water deeper into the floor. The grout cracks further. The tile eventually lifts completely.
3. Grout That Crumbles When You Touch It
Run your finger along the grout lines in your shower. Does the grout feel sandy? Does it leave powder on your fingertip? That grout has lost its structural integrity. It is no longer sealing anything. Water is passing through it as easily as air passes through a screen door.
Crumbling grout is not something you fix with a tube of silicone from Bunnings. The deteriorated material needs to be cut out completely and replaced with a properly applied grout, ideally an epoxy-based product like Mapei epoxy grout, which Mr Grout uses for its superior water resistance and durability.
4. Mould That Keeps Coming Back No Matter How Much You Clean
You have scrubbed. You have bleached. You have tried every mould-killing product on the shelf. Two weeks later the black spots are back in exactly the same places. This is not a cleaning problem. It is a moisture problem.
Mould behind the grout, or mould that feeds on water constantly seeping through cracked grout joints, will return indefinitely until the source of moisture is cut off. The cleaning products are treating the symptom. Replacing the grout treats the cause. Learn more about why mould keeps coming back in bathroom grout.
5. A Musty Smell That Will Not Go Away
Your bathroom should not smell. If you walk in and catch a damp, earthy, or musty odour that lingers even with the window open and the exhaust fan running, there is trapped moisture somewhere. In a tiled shower, the most likely hiding spot is the cavity behind the tiles, fed by water seeping through failed grout.
That smell is often the first warning sign. It appears before visible damage, before water stains, before tiles lift. Do not ignore it.
6. Discoloured or Darkened Grout Lines
Grout that has absorbed water over a long period will darken unevenly. You might notice patches where the grout looks permanently wet, or sections that have turned a shade darker than the rest of the shower. This is not a cosmetic issue. It means water is sitting inside the grout rather than beading on the surface, and that water is being drawn deeper into the wall cavity with every shower.
7. Cracking Along the Corners Where the Walls Meet the Floor
The joint where your shower wall tiles meet the floor tiles is called the perimeter joint, and it is the single most vulnerable point in any shower. It takes the full weight of every person who steps in and out. It expands and contracts with changes in temperature and humidity. When the silicone or grout along this joint cracks, water has a direct channel into the floor underneath.
Surface silicone can sometimes patch this temporarily, but if the cracking keeps returning, the underlying grout and movement joint have likely failed and need professional attention.
Why It Is Probably Not Your Plumbing
We see it all the time. A homeowner calls a plumber. The plumber pressure-tests the pipes, checks the drainage, inspects the taps and the shower head, and finds nothing. The pipes are sound. The leak is still there. That is because the water is not coming from inside the plumbing. It is coming from the shower floor, passing through the grout, and travelling into the surrounding structure.
Plumbers fix pipes. Grout specialists fix what is between the tiles. They are different trades, and calling the wrong one first costs you a callout fee and a week of delay while the damage gets worse.
What Happens If You Wait?
The timeline is predictable. Year one: a small crack in the grout. Year two: water begins pooling beneath the tiles. Year three: the adhesive fails, tiles start lifting, and timber subfloors begin to rot. By the time you see water staining the ceiling below, the damage to the subfloor and surrounding framework can already run into the thousands.
The earlier you catch it, the simpler and cheaper the fix. Most leaking showers caught at the grout-deterioration stage can be repaired in a single visit without removing a single tile.
Get Certainty, Not a Guess
You do not need to figure this out alone. A professional inspection from Mr Grout takes the guesswork out of the equation. We assess the shower, identify exactly where water is getting through, and give you a fixed-price written quote on the spot. No obligation. No pressure. Just clarity on what is actually happening behind your tiles.
If you are in Brisbane, our local specialists handle grout repair Brisbane wide with same-day inspections and quotes. On the Gold Coast? Visit our Gold Coast grout repair page to book your inspection.
Already spotted a few of these signs? Call us on 0488 801 015 or book your inspection online. The sooner we look, the less it costs to fix.