What happens inside a pressurised pipe when it starts to leak?

Full transcript

George and Dave in conversation. Every word of the episode, exactly as recorded.

George

Welcome to the ADI Leak Detection podcast. I'm here with Dave from ADI Leak Detection, the UK's leading leak detection specialists, who's here to answer your questions and provide expert leak detection advice. Dave, today's question is one I think a lot of homeowners with a combi boiler or an underfloor heating system will recognise, how does acoustic leak detection actually work on a pressurised water or heating system?

Dave

Great question. So the short version is this: when water escapes from a pressurised pipe through a crack or a pinhole, the escaping water generates sound energy. Acoustic leak detection uses sensitive listening equipment to pick up that sound and trace it back to its source.

George

And we're talking about sounds you can't hear yourself, right? You can't just press your ear to the floor.

Dave

Exactly. The frequencies we're listening for are often well outside what the human ear picks up unaided. ADI's engineers use ground microphones and acoustic listening rods, a listening rod is basically a contact sensor you place directly on a pipe, a valve, or even a floor surface, and they amplify the signal so the engineer can hear what's happening inside the system.

George

So the equipment is doing the heavy lifting. What does the signal actually sound like, and how do you know it's a leak rather than, say, the boiler firing up?

Dave

That's where experience counts. A pressurised leak produces a fairly characteristic hiss or rushing noise, and it's consistent, it doesn't come and go the way a pump or a filling valve would. ADI's engineers learn to read those sound signatures over time, so they can distinguish a genuine breach from background noise pretty reliably.

George

Does the pipe material make a difference? I've got copper in my kitchen but I know a lot of newer homes have plastic push-fit.

Dave

It makes a significant difference, yes. Metal pipe, copper especially, conducts sound really well, so the signal travels further along the pipe and it's easier to follow. Plastic pipe absorbs much more of the sound energy, which means the signal degrades faster. Our engineer has to work in shorter intervals, listening more frequently along the run to make sure they don't miss the peak signal point.

George

And what about surface types? If the pipe's under a solid concrete floor versus a suspended timber floor, does that change how you work?

Dave

It does. A solid floor actually helps transmit the acoustic signal up to the surface, so a ground microphone placed on concrete or tile can pick up a leak beneath it reasonably well. Timber floors are more variable, there's more interference from the void underneath and the boards themselves. On a timber floor the ADI engineer will typically try to access the pipe directly, either through a floorboard or an access point, rather than relying purely on surface listening.

George

What about heating systems specifically? A pressurised sealed heating circuit is a bit different from a mains water supply pipe, there's less pressure, I think?

Dave

Correct. Mains supply pressure is higher, so the acoustic signal at the leak point tends to be stronger and easier to detect. A sealed heating circuit typically runs at somewhere between one and two bar, which is lower, and that means the sound energy produced at the breach is quieter. Our engineers account for that by using the most sensitive settings on the equipment and by being very systematic about where they listen along the circuit.

George

Is acoustic detection always enough on its own, or are there situations where you'd bring in another method as well?

Dave

Acoustic listening is often the starting point because it's non-invasive and it covers a lot of ground quickly. But there are situations, deeply buried pipes, heavily insulated systems, plastic pipework with a very weak signal, where ADI's engineers will combine acoustic work with tracer gas testing or pressure testing to confirm the location before any floor or wall is opened up. The aim is always to give the homeowner a precise location, not a best guess.

George

That's really useful context. So you're not just listening and hoping, there's a process behind it.

Dave

Absolutely. Acoustic leak detection on a pressurised system is a methodical process: the ADI engineer isolates sections of the circuit, takes readings at multiple points, and maps where the signal is strongest. That peak signal point is where the leak is. It avoids a lot of unnecessary excavation, and homeowners genuinely notice the difference.

George

Dave, that's a really clear explanation, thank you. If your water meter's spinning, your heating pressure keeps dropping, or you've got damp appearing from nowhere, ADI Leak Detection is one of the country's most trusted names in residential leak detection. We'll see you next time.

How this episode was made. This episode was produced using AI-generated voices and script, based on real leak detection questions and the working knowledge of ADI Leak Detection engineers.