Signs of a hidden leak, and how to confirm one

Most leaks we find were running for months before anyone called. A drip under a sink is easy to spot. A pinhole in a pipe under a concrete floor or inside a wall can waste thousands of litres and soak the structure long before a stain appears. The earlier you catch one, the smaller the repair.

The signs, from the most common

A water bill that jumps. If your usage has not changed and the bill has gone up by a quarter or more, water is going somewhere. Compare the same months across two years.

Stains, bubbling paint, or swollen plaster. A yellow or brown ring on a ceiling, paint that blisters, or plaster that feels soft under a thumb. On a ceiling, the stain is often not directly under the leak: water runs along a joist or pipe before it drips.

A musty smell that does not go away. Damp timber and plaster smell like a cellar. If a room smells that way with the windows open and nothing visible, the damp is inside a wall or under the floor.

A warm spot on a slab floor. In homes with hot water pipes under a concrete floor, a leak on the hot side warms the slab above it. Walk barefoot: a patch that is warmer than the rest of the room is worth a call.

The sound of running water. Stand in the quietest room at night with every tap off. A hiss or a trickle inside a wall means water is moving where it should not.

Loose or cracked floor tiles. Water under tiles softens the adhesive. Tiles start to sound hollow when you tap them, then lift or crack, often near a bathroom or kitchen wall.

Mould behind furniture. Black spots on the wall behind a wardrobe or a sofa, on a wall with pipes in it, point to damp from inside, not just from poor airflow.

Low water pressure. A leak large enough to notice on the meter often lowers pressure at the taps as well.

Confirm it with the water meter

The meter test takes half an hour and costs nothing.

What a leak detection visit does

The old way to find a hidden leak was to open walls until you found it. Today a technician narrows it down first, so the wall or floor is opened in one place only.

Acoustic listening. Water escaping under pressure makes a sound. A ground microphone and headphones pick it up through concrete and tiles, and the sound is loudest right above the leak.

A thermal camera. On hot water pipes, and on walls damp from a leak, the camera shows a temperature pattern that follows the water.

A moisture meter. It reads how wet a wall or floor is without making a hole, and maps where the damp starts and how far it has spread.

A pressure test. Each section of pipe is isolated and pressurised. A section that loses pressure is the one with the leak.

If the meter moved, or you have two or more of the signs above, book a leak detection visit. The technician will find the source before anything is opened, and can usually make the pipe repair on the same visit.