How to Tell If You Have a Hidden Water Leak

The easiest way to tell if you have a hidden water leak is to run a water meter test: turn off every tap and water-using appliance, then check whether your meter is still ticking over. If it is, water is escaping somewhere you can't see. Other signs include an unexplained jump in your water bill, damp patches, mould, a musty smell, or a drop in water pressure. Here's how to spot a hidden leak early — before it damages your home.

The warning signs of a hidden leak

Hidden leaks happen inside walls, under floors or beneath your slab, so you often notice the symptoms before you ever see water. Watch for these:

A higher water bill with no change in how much water you're using. This is one of the most reliable early signs — the Water Corporation bill goes up but your habits haven't.
Damp patches or discolouration on walls, ceilings or floors, sometimes with paint bubbling or peeling.
Mould or mildew appearing in a spot that shouldn't be wet, or a persistent musty smell.
Reduced water pressure when a pipe is losing water before it reaches your taps.
The sound of running water when everything is switched off.
Warm spots on the floor, which can indicate a leak in a hot water line under the slab.
Cracked or lifting tiles and unusually green, lush patches in the garden over a buried pipe.

The water meter test (do this yourself)

This simple test confirms a leak in a few minutes and needs no tools. Here's how to run it:

Turn everything off. Close all taps inside and out, and make sure no appliances (dishwasher, washing machine, irrigation) are running.
Find your water meter. In Perth it's usually near the front boundary of the property, often in a box in the ground. Note the exact reading, including the small dials.
Wait 1–2 hours without using any water.
Check the meter again. If the reading has moved with everything off, you have a leak somewhere on your property.

Some meters have a small red or black leak indicator dial that spins when even a tiny amount of water is flowing. If it's turning with all taps off, that's a clear signal. Not sure where your meter is? Our guide on finding and turning off your water mains shows you exactly where to look.

What to do while you wait to confirm

If your meter test is inconclusive — the reading barely moved, or you're not certain — repeat it overnight when no one is using water. A leak will show more clearly over a longer period. It also helps to rule out the obvious first: check that a garden tap isn't dripping, that the irrigation or reticulation controller isn't running a cycle, and that no appliance is quietly filling. Ruling those out narrows things down to a genuine hidden leak, which is where professional detection earns its keep.

Toilet leaks: the silent water waster

A leaking toilet can waste thousands of litres and add to your bill without a single visible drip. To test it, put a few drops of food colouring in the cistern and wait 15 minutes without flushing. If colour appears in the bowl, water is leaking from the cistern through to the bowl and the seal or valve needs attention. It's a small toilet and fixture repair that pays for itself quickly.

Common places hidden leaks happen

Knowing where leaks tend to hide helps you spot them sooner. The usual suspects in a Perth home are:

Under the slab. Pipes buried in or beneath the concrete slab can leak for months undetected, often showing up as a warm patch or an unexplained bill.
Inside walls. Pipe joints behind plaster can weep slowly, causing damp patches and bubbling paint before any water is visible.
Under sinks and vanities. Worn seals and loose fittings drip inside cabinets where you don't look often.
At the hot water system. A tank or connection starting to fail can leak quietly at the base.
In the irrigation or reticulation system. Underground garden lines are a very common source of a mysterious jump in usage.

Why hidden leaks matter

A hidden leak isn't just a bigger bill. Left alone, it can cause:

Structural damage to timber, plaster and flooring
Mould that affects air quality and health
Damage to your home's foundations or slab
Wasted water — a genuine issue in WA's climate

The sooner it's found, the smaller the repair. A slow leak that's caught this month is a patch; the same leak left for a year can mean replacing flooring and cabinetry.

How professional leak detection works

Once you know there's a leak, the hard part is finding it without ripping up walls or floors. That's where professional water leak detection comes in. Licensed plumbers use non-invasive tools such as acoustic listening equipment, thermal imaging and pressure testing to pinpoint the exact spot. That means the repair is targeted and minimal, rather than exploratory digging or demolition.

If the leak turns out to be a cracked or corroded pipe, it can be repaired before it becomes a burst pipe and a much bigger job.

When to call a plumber

Call a licensed plumber if your meter test confirms water is moving with everything off, your bill has jumped for no reason, or you can see damp, mould or warm spots you can't explain. Trying to chase a hidden leak yourself usually means unnecessary damage — professional detection finds it fast and keeps the repair small.

Suspect a leak you can't see? Call our licensed Canning Vale plumbers and we'll locate it without tearing your home apart.

Frequently asked questions

How do I check for a hidden water leak myself?

Run a meter test. Turn off every tap and water-using appliance, note your water meter reading, wait one to two hours without using water, then check again. If the reading has moved, water is escaping somewhere on your property.

Can a hidden leak increase my water bill?

Yes — often significantly. An unexplained jump in your Water Corporation bill, with no change in your usage, is one of the most reliable signs of a hidden leak. Even a small constant drip adds up to thousands of litres over time.

How do plumbers find a leak without digging?

Licensed plumbers use non-invasive tools like acoustic listening devices, thermal imaging cameras and pressure testing to pinpoint the exact location. This means the repair is targeted, so there's far less digging, demolition or disruption to your home.

How can I tell if my toilet is leaking?

Put a few drops of food colouring in the cistern and wait about 15 minutes without flushing. If coloured water appears in the bowl, the cistern is leaking through to the bowl and the seal or valve needs a simple repair.