How Does Acoustic Leak Detection Work?

Water escaping under pressure creates a distinct noise as it hits surrounding pipe walls, soil and building materials. Acoustic leak detection captures that noise and turns it into a workable location, so you fix the pipe and not the whole floor.

What sound does a water leak actually make?

A pressurised leak produces a continuous hissing, rushing or drumming sound as water forces its way out of a pipe. The pitch and volume change depending on the pipe material, water pressure, depth and the surface above. Metal pipes carry sound further and louder than plastic, while a leak under a solid concrete slab transmits differently to one beneath timber floorboards. Technicians learn to distinguish genuine leak noise from background sounds such as traffic, appliances and central heating.

What equipment is used for acoustic leak detection?

Acoustic leak detection relies on ground microphones, contact sensors and electronic amplifiers that make faint underground sounds audible and measurable. The core tools include:

• Ground microphones placed on hard surfaces to detect vibration through floors and paving.
• Contact rods and sensors pressed against exposed pipework, radiators and stopcocks.
• Electronic correlators that compare the sound arriving at two points to calculate the leak position.
• Noise loggers left in place to capture intermittent leaks over time.
• Headphones and digital displays that filter out ambient noise and highlight the true leak signal.

How does the leak detection process work step by step?

The process follows a logical sequence designed to narrow down the leak from the whole property to a single point.

1. The technician gathers history: when damp appeared, pressure loss on the boiler, and any recent works.
2. The system is isolated and pressure tested to confirm a leak exists and roughly where.
3. Ground microphones and sensors sweep the suspected area to find the loudest, most consistent signal.
4. A correlator or noise logger confirms the position where two readings converge.
5. The exact spot is marked so any excavation or repair is targeted and minimal.

We combine acoustic methods with thermal imaging and moisture mapping where useful, because no single technique suits every leak. This layered approach forms part of our wider leak detection service across London.

When does acoustic detection work best, and when does it not?

Acoustic detection works best on pressurised pipes carrying mains or heating water, where the escaping flow generates constant noise. It is highly effective on metal pipework, under hard floors and in quiet conditions. It is less reliable on gravity-fed waste and drainage, on very low pressure systems, or where the leak is so slow it makes almost no sound. In those cases technicians turn to tracer gas, thermal imaging or camera inspection instead. Signs that point towards a hidden pressurised leak include:

• Unexplained drops in boiler pressure that need frequent topping up.
• Warm patches on floors above heating pipes.
• A water meter that keeps turning with all taps off.
• Persistent damp, staining or mould with no obvious source above.
• The faint sound of running water when the property is silent.

How does leak detection connect to a damp and mould survey?

A leak is often the hidden cause behind damp and mould, so finding it is only half the job. Water tracking through walls and floors leaves staining, salting and mould that continues after the pipe is fixed. Our comprehensive damp and mould survey costs a fixed £500 and gives you a full insurance-ready written report with a photographic evidence appendix, clear findings and prioritised recommendations. That means you can see exactly what caused the problem, how far the damage spread, and the order in which to put it right.

What affects the cost of fixing a leak once it is found?

The cost of repair depends on where the leak sits, how deep it is and what has to be moved to reach it. A leak under a suspended timber floor is usually simpler to access than one beneath a thick concrete slab or a tiled bathroom. The pipe material, the extent of damp damage already caused, and whether flooring or plaster needs reinstating all influence the final figure. We set these factors out in words in your report so you understand what drives the work, without guessing at numbers before the leak is confirmed.

If you've got damp, mould, or a leak — you already know it needs sorting.

The longer it sits, the worse it gets. Most investigations are booked within 48 hours.