1. Running water in a quiet house

Stand in the hallway late at night with everything switched off and listen. A faint hiss or trickle with no tap open is one of the most reliable indicators there is, and it often appears months before any visible damage. Put an ear to the wall in a few places and the sound usually gets louder near the source.

2. A patch of lawn greener than the rest

If the supply line runs under the garden, a leak feeds the grass above it. A strip or patch that stays lush in dry weather, or ground that feels soft underfoot when it has not rained, is pointing directly at the pipe beneath.

3. Tap water that tastes or smells different

A leak on a buried supply line can draw soil and bacteria in through the same opening water escapes from, particularly when pressure drops. A sudden earthy or metallic taste from a tap that was fine last week deserves checking rather than filtering.

4. Paint or wallpaper that bubbles

Moisture arriving from behind lifts a decorated surface away from the wall before it ever stains it. Blistering paint, a seam of wallpaper peeling on its own, or a bulge in plasterboard all mean water is already in the structure.

5. Mould that keeps returning to the same spot

Mould cleaned off a wall and back within a fortnight is not a ventilation problem. Something is keeping that area permanently damp, and in a bathroom or kitchen it is very often a joint behind the tiling rather than condensation.

6. The pump or boiler cycling more often

A system that loses pressure continuously has to work harder to hold it. If your boiler needs topping up more frequently than it used to, or a pressure pump is starting several times an hour with nothing running, water is going somewhere.

“By the time a hidden leak is visible, it has usually been running long enough to have done the expensive part of the damage already.”

7. Confirm it with the meter test

Turn off every tap and appliance in the house, including the ice maker and any irrigation. Note the exact meter reading, wait two hours without using water, and read it again. Any movement means an active leak somewhere on your side of the meter.

That test costs nothing and rules the question in or out completely. If it moves, book a leak detection visit rather than opening walls — acoustic and thermal equipment will find the spot in under an hour without taking anything apart.