How to find a water leak in your home

Some leaks are obvious. Others remain behind walls, under floors or underground until they cause damp, mould or a high water bill.

Published 2 October 2026

Common signs of a hidden leak

Look for damp patches, peeling paint, mould that returns after cleaning, low water pressure, the sound of running water when taps are off, or an unexplained rise in water use.

Check visible fittings first

Inspect beneath sinks, around toilets, beside appliances and near the boiler. Look for drips, staining, swollen cabinets or wet pipe joints. Do not remove fixed panels or disturb electrical fittings.

Use the water meter as a simple check

Turn off taps and water-using appliances. Note the meter reading, wait without using water, then check it again. Movement can point to water escaping somewhere in the property. Shared supplies and some appliances can affect this check, so it does not locate the leak by itself.

Act quickly if water is escaping

Turn off the water at the stopcock if it is safe to do so. Keep away from wet electrical fittings. Move belongings away from the affected area and call an emergency plumber when water is actively causing damage.

How a specialist locates a hidden leak

A specialist chooses the method that fits the pipework and the symptoms. SJW can use thermal imaging, acoustic testing or tracer gas to narrow down the source without unnecessary damage.

Check insurance before trace and access work

If you may claim under home insurance, contact your insurer before work starts. Ask what evidence and approval it needs. Cover varies, and finding the leak can be treated differently from repairing the failed pipe.

Book leak detection in London

When the source is not visible, read about SJW's leak detection service or send photographs and a short history through the quote form.