How to Find a Water Leak in Your Home (UK Guide)

Reviewed by the DCI Leak Detection team · Last updated June 2026

A water leak you cannot see is one of the most frustrating problems in a home. The bill creeps up, a patch of damp appears, or something just sounds wrong, yet there is nothing obvious to point at. Finding a leak follows a clear order: read the signs, run a simple meter test, check the places you can reach, and bring in detection for the ones you cannot. This guide walks through each step.

Signs you have a water leak

Most leaks announce themselves long before you find them. The trick is knowing what to notice. If two or three of these signs line up, it is well worth running the meter test in the next section.

• A water bill that keeps rising. If you are on a meter and the bill climbs without you using more, water is going somewhere. A small unexplained jump is one of the most reliable early signs, which is why a leak can hide behind a bill long before you see any damp. We cover this in detail in our guide to a high water bill with no visible leak.
• Damp patches, stains or mould. A spreading damp mark on a wall, floor or ceiling, peeling paint, or a musty smell that will not shift all suggest water is escaping nearby. Mould that keeps coming back after you clean it is often feeding on a hidden leak.
• A drop in water pressure. When water escapes before it reaches your taps, the flow at the tap weakens. A sudden, unexplained drop in pressure across the home is a recognised sign of a leak.
• The sound of running water. A faint trickle, hiss or running-water sound when every tap is off points to water moving through a pipe it should not be. Noisy pipes are another common clue listed by the water companies.
• Warm spots on the floor. A warm patch on a tiled or solid floor, or an area that dries first, can mean a leaking hot-water or central heating pipe beneath it.
• A patch of lush, faster-growing grass. Outside, an unusually green or boggy patch over the supply pipe can flag an underground leak, even in dry weather.

South West Water, which supplies Cornwall and Devon, and other suppliers such as Southern Water list the same core signals: an unexplained rise in a metered bill, a drop in pressure, noisy pipes and damp patches. None of these on its own proves a leak, but together they tell you to investigate.

The water-meter test

The single most useful thing you can do at home is the water-meter test. It tells you whether water is leaving the system when nothing is being used, which is the clearest sign of a leak on your side of the meter.

1. Turn everything off. Close every tap, make sure no appliance is running, and check that no toilet is refilling. Nothing should be using water.
2. Read the meter. Note the exact reading, including the small dials or the spinning sweep hand if your meter has one.
3. Leave it alone. Do not use any water for a few hours, or simply take a reading last thing at night and another first thing in the morning.
4. Read it again. If the reading has moved, or the sweep hand has crept round, with no water used, you almost certainly have a leak.

To narrow it down, turn off your internal stop tap and repeat the test. If the meter keeps moving, the leak may be between the meter and the stop tap, which is usually the water company's concern. If it stops, the leak is inside the property, after the stop tap, and that part is yours to sort. South West Water and other suppliers set out this same before-and-after method. For a step-by-step version with photos of meter types, see our guide on how to check your water meter for a leak.

For context on what counts as "normal" movement, the average person in the UK uses roughly 139 to 142 litres of water a day, according to the Consumer Council for Water and Water UK. A meter ticking over with the whole house quiet and asleep is not normal use, it is a leak.

Where to check around the house

Once the meter has confirmed something is wrong, check the spots you can actually see and reach. You may find an easy fix before you need anyone in.

One word of caution before you blame a leak for every bit of damp: condensation can look similar. It tends to be a widespread misty damp or small beads over a large area, usually in cold weather, and it leaves no lasting mark. A real leak leaves a defined patch that tracks back to one point and often dries to a brown or yellow stain. If the damp keeps returning or growing, treat it as a leak.

Why some leaks stay hidden

If you have run the meter test and checked everywhere you can reach but still found nothing, you are dealing with a hidden leak. These are common, and they are exactly why leak detection exists.

Water takes the path of least resistance. A leak under a solid floor, inside a stud wall or in a heating pipe buried in a screed can run for weeks with almost nothing to see. When it does show, the water has often travelled along a joist, a pipe run or the back of the plasterboard before dripping out, so the damp patch sits well away from the actual source. Pressurised supply and heating pipes make this harder still: the leak can be slow, or only show when the heating fires up. That is why guessing where to dig or cut usually causes more damage than the leak itself. Our guide to finding a leak in walls or ceilings goes deeper into these tricky cases.

How professional detection finds them

Professional leak detection is non-invasive, which means the leak is located before anything is cut open. A specialist uses several methods together, each one cross-checking the others, to build a picture of where the water is really coming from.

• Thermal imaging. A thermal camera reads small temperature differences across a floor, wall or ceiling. A hot-water or heating leak shows as a warm trail, and a cold supply leak as a cool one, mapping the spread back towards the source.
• Acoustic detection. Sensitive microphones and correlators pick up the sound a pressurised leak makes as water escapes, which helps locate a buried pipe under a floor or in the ground.
• Tracer gas. A safe gas is introduced into the pipework and rises to the surface at the exact point it is escaping, pinpointing the small or slow leaks that are otherwise almost impossible to find.
• Moisture meters. These confirm how far the dampness has tracked and where it is wettest, narrowing the search to the true source rather than where the water happens to show.

Together, these tools turn a guessing game into a targeted job. If a small section does need opening, it is one neat access point at the confirmed leak, not a torn-out floor or ceiling. Our main water leak detection service page explains how we approach a job from first call to report.

When to call a professional

Plenty of leaks are simple, like a dripping tap or a worn washer, and you can sort them yourself. Bring in a professional when the leak is hidden or the situation needs care. Call one when:

• the meter keeps moving with all the water off, but you cannot see where it is going;
• damp keeps coming back, or a stain grows even slowly;
• your pressure or your bill has changed and there is no obvious reason;
• water is near light fittings or wiring. In that case, do not touch the fitting and switch off the electricity at the fuse box if it is safe, as Electrical Safety First advises, leaving the power off until it has been checked;
• you need an insurer-ready report to claim for the damage.

On that last point, many home policies include trace and access cover, which pays to find a hidden leak and make good the damage caused by reaching it, with limits that typically start around five thousand pounds and rise to around ten thousand on some policies. It does not usually pay to repair the pipe itself, and cover varies by insurer, so check your policy. A proper report makes the difference to a claim, and our trace and access service provides the documentation insurers look for. Finding a leak early keeps the damage, and the eventual repair, smaller.

Frequently asked questions