Signs of a hidden leak, and what to do about each one

A metered bill that doubles with no change in how you use water almost always means water is escaping somewhere between the meter and your taps.

Turn every tap and appliance off, then watch the meter. If it still moves, water is leaving the pipework somewhere.

A sealed heating system that needs topping up every few days is losing water through a leak in the circuit, not evaporating.

A floor that is warm in one spot with no underfloor heating, or a heated floor with one area hotter than the rest, points to a hot pipe leaking beneath it.

A patch on a ceiling or wall that dries out and returns is being fed from a pipe, and the pipe is rarely directly behind the stain.

Pressure that has dropped over weeks, especially at the kitchen cold tap, can mean the supply pipe is leaking underground.

Water escaping under pressure makes a faint hiss. If you can hear it at night with everything off, so can our microphone.

A persistent damp smell, mould on skirting or lifting flooring usually means water has been sitting under the floor for some time.