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Signs of a Hidden Water Leak in Your Home
Reviewed by the Devon Leak Detection team. Last updated June 2026
The short answer
The clearest signs of a water leak are a rising water bill, a damp patch that keeps coming back, the sound of running water with every tap off, a warm patch on the floor, and a meter that keeps ticking when nothing is in use. If you spot any of these, it is worth having the leak traced before damage spreads.
A hidden leak rarely announces itself. The pipe is usually buried in a wall, under a floor or beneath the garden, so the first thing most people notice is a side effect rather than the water itself. The good news is that the warning signs are fairly consistent, and once you know what to look for you can usually tell whether something is wrong long before a ceiling sags or a floor lifts.
Below is a plain checklist of the symptoms we see most often in Devon homes, what each one tends to point to, and the simple checks you can run yourself before deciding it is time to call someone in.
Your water bill has crept up for no reason
An unexplained jump in your metered bill is one of the most common ways a hidden leak gives itself away. If your usage has climbed but your household routine has not changed, water is going somewhere it should not. A continuous leak runs day and night, so even a slow weep adds up quickly over a billing period.
Before you assume the worst, rule out the obvious: a recent house guest, a garden you have started watering, or a new appliance. If none of those explain it, the rise is a strong hint that a pipe or fitting is losing water somewhere you cannot see.
A damp patch that keeps coming back
A stain on a wall or ceiling that you wipe down, dry out and then watch return is a telling sign. Condensation and one-off spills dry and stay dry. A patch that reappears, especially in the same spot, is usually being fed by a steady source behind the surface.
Pay attention to where the damp sits. A patch low on a wall can point to a leaking supply pipe in the floor void, while a stain on a ceiling often sits below a bathroom or a run of pipework upstairs. The water frequently tracks along a joist or a pipe before it shows, so the visible mark is not always directly under the leak itself.
The sound of running water with the taps off
If the house is quiet and you can still hear a faint trickle, hiss or hum from a wall or under the floor, it is worth investigating. Pressurised water escaping from a pipe makes a steady noise that you would not normally hear with everything switched off.
Try it at night when the house is settled and the street is quiet. Stand still in different rooms, put an ear near skirting boards or the airing cupboard, and listen. A persistent sound with no tap, toilet or appliance running is a classic pointer towards a supply pipe losing water.
A warm patch on the floor
An area of floor that feels noticeably warmer than the rest often points to a leak on a hot water or heating pipe below it. This is especially common in homes with underfloor heating, where a failing joint or pipe lets warm water escape into the screed and heat the surface above.
Other clues tend to travel with it: heating that takes longer to warm up, a boiler or system that keeps losing pressure and needs topping up, and uneven warmth across a room. If you are nudging the system pressure back up every few days and a patch of floor is warm to the touch, a hidden hot pipe leak is a likely culprit and worth tracing carefully so the floor is not opened up unnecessarily.
A water meter that keeps ticking
Your meter is one of the most reliable tools you have. With every tap, toilet and appliance switched off, take a look at it. If the dial is still turning, or the digits are still climbing, water is moving through your system even though nothing is in use. That movement has to be going somewhere.
You can narrow down where the leak sits using your internal stopcock, the valve that controls water coming into the property. Turn it off and watch the meter again. If the meter stops, the leak is likely on your side of the stopcock, somewhere inside or under the house. If it keeps moving with the stopcock closed, the leak may be on the supply pipe between the meter and the property. As a rough guide, a faster-spinning dial suggests a larger leak and a slow creep suggests a smaller one. For a free guide to the wider process, see our page on water leak detection.
A musty smell or unexplained mould
A damp, earthy smell that lingers in a room, a cupboard or a hallway can be an early warning before any stain appears. Trapped moisture from a slow leak feeds mould and mildew, and the smell often arrives first. If a corner of a room smells musty no matter how often you air it, there may be water collecting out of sight.
Black or green mould creeping along a skirting board, around a window reveal or low on a wall can have several causes, but where it appears alongside other signs on this list, a hidden leak moves up the list of suspects.
A drop in water pressure
If your shower has lost its push or the bath takes longer to fill than it used to, and the change has come on gradually, a leak may be bleeding off pressure before the water reaches your taps. A pipe losing water upstream means less of it arrives where you want it.
Low pressure has plenty of innocent explanations too, from work being carried out on the network to a partly closed valve. But a steady, unexplained decline, particularly when it lines up with a higher bill or a damp patch, is worth taking seriously rather than living with.
When to get a leak traced
One sign on its own may have a simple explanation. Two or more together, or a single sign that will not go away, is the point to act. A leak does not fix itself, and the longer water sits behind a wall or under a floor the more it costs to put right, both in repairs and in wasted water.
This is where professional leak detection earns its keep. Rather than guessing and pulling up floors, specialists use methods such as acoustic listening equipment, thermal imaging and tracer gas to pinpoint the source first, so any opening up is kept to a minimum. Many home insurance policies include trace and access cover, which is designed to help with the cost of finding the leak and making good afterwards, though it typically does not cover repairing the pipe itself. It is always worth checking your own policy wording. If you are weighing up your options, our guide to spotting the early signs sits alongside the practical detection work we carry out across Devon.
Frequently Asked Questions
Switch off every tap, toilet and appliance, then watch your water meter. If the dial keeps turning or the digits keep climbing with nothing in use, water is escaping somewhere. Pair that with checks for damp patches, musty smells and the sound of running water for a clearer picture.
Yes. A hidden leak runs continuously, day and night, so even a slow weep adds up over a billing period. If your usage has climbed but your household routine has not changed, an unexplained rise in a metered bill is often one of the first signs that water is going to waste.
A warm area of floor often points to a leak on a hot water or heating pipe beneath it, which is common with underfloor heating. If it comes with a system that keeps losing pressure and needs topping up, a hidden hot pipe leak is a likely cause and worth tracing carefully.
Many home insurance policies include trace and access cover, which helps with the cost of locating a leak and making good afterwards. It typically does not cover repairing the pipe itself or the water damage, so it is always worth reading your own policy wording or asking your insurer directly.
It is better to act than to wait. A leak does not resolve on its own, and the longer water sits behind a wall or under a floor the more damage it causes and the more it costs to fix. If a sign keeps returning, or two or more appear together, it is sensible to have the leak traced.
Think you have a hidden leak? Let us find it.
We trace leaks accurately across Devon, so any disruption to your home is kept to a minimum.