Water leaks are responsible for a significant amount of property damage in the UK every year — and the majority of that damage comes not from the initial leak but from how long it goes undetected. A slow leak inside a wall or under a floor can run for weeks before it becomes visible, by which point the damage to plasterwork, joists and insulation is already done.
Knowing what to look for can save you thousands. Here's how to spot a leak early and what to do when you find one.
Warning signs you have a water leak
Your water bill has gone up unexplained
If your water usage habits haven't changed but your bill has increased, you may have a slow leak somewhere in the system. Even a small drip — invisible to the naked eye — can waste hundreds of litres per week. This is one of the earliest and most reliable indicators.
Damp patches, staining or bubbling paint
Damp appearing on a wall or ceiling that doesn't correspond to a bathroom directly above, or paint that's bubbling and peeling without an obvious external cause, often points to a leaking pipe inside the structure. Discolouration around the base of walls is another sign.
Musty smell in a room
Water sitting inside walls, under floors or beneath kitchen/bathroom units promotes mould growth quickly. If a room smells persistently damp or musty even after airing, and you can't find an obvious source, check for a hidden leak.
Low water pressure
A sudden unexplained drop in water pressure — particularly if it affects the whole property rather than just one outlet — can indicate a break or significant leak in the supply pipe. If your property is on an older lead or iron supply, this is worth investigating promptly.
Sound of running water when nothing is on
If you can hear water moving somewhere in the property when every tap, toilet and appliance is off, you have an active leak. The sound might be faint — a trickle behind a wall or under a floor — but trust it.
Hot spots or cold spots on floors
An underfloor heating system or a hot water pipe running beneath the floor can cause warm patches on the floor above when it's leaking. Conversely, a cold spot on a floor where you'd expect warmth can indicate that water is pooling.
Meter reading that won't stay still
This is the definitive test — see below.
The water meter test
If you suspect a leak, this is the most reliable way to confirm it:
- Turn off every tap, toilet, appliance and outside supply in the property
- Find your water meter — usually in a pavement box outside, or under the kitchen sink
- Note the exact reading, including the low-flow indicator (usually a small dial or digital display that moves with very low flow)
- Do not use any water for 30 minutes
- Check the reading again — if it has moved, you have a leak on the supply side
If the meter moves even with the internal stopcock turned off, the leak is on the external supply pipe between the meter and your property — which is your responsibility in most cases under UK law.
What to do when you find a leak
Turn off the water supply immediately. Your internal stopcock is usually located under the kitchen sink, where the water main enters the property, or in an airing cupboard. Turning it off stops the flow and limits damage. If you can't find your stopcock, the external stop valve on the pavement — which requires a special key — is the next option.
Turn off the electrics if water is near consumer units, sockets or appliances. Water and electricity together are dangerous. If water is dripping near any electrical installation, switch off the relevant circuit at the fuse board or the whole board if you're not sure.
Take photos. Before any cleanup, photograph the damage. This matters for insurance claims.
Call a plumber. Leak tracing and repair requires the right equipment — acoustic listening devices, thermal imaging, and tracer gas in some cases. We include leak tracing in our standard visit as part of the diagnostic assessment, so there's no additional charge for identifying where the leak is coming from.
How leak tracing works
For visible leaks — a dripping pipe, a joint that's let go — the source is obvious and the fix is straightforward. For hidden leaks inside walls, under floors or in the ground, specialist equipment is needed.
We use acoustic leak detection to pick up the sound signature of water escaping under pressure, and thermal imaging to identify temperature differences in surfaces where water is present. This lets us pinpoint leaks without unnecessary damage to your property — no pulling up floors or knocking through walls to find out where to look.
When it's an emergency
A burst pipe, uncontrolled water entering the property, or a leak near electrical installations are emergencies. Our out-of-hours emergency rate is £125 + VAT and covers attendance between 6pm and 8am, weekends and bank holidays — with a fixed quotation provided on site before any repair begins.
For non-urgent leak investigation, our standard visit fee is £75 + VAT. We'll attend, locate the leak, and give you a fixed price for the repair. If you proceed, the visit fee comes off the total.
Call 0208 092 1359 for immediate assistance, or send us photos and details via WhatsApp if you'd like a remote assessment first. We cover Hertfordshire and North London from our Watford base.