Why does my moisture meter show high readings but I can't find the 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, leading leak detection specialists across the UK, who's here to answer your questions and provide expert leak detection advice. Dave, today's question comes straight from a homeowner who's been told their moisture readings are elevated but nobody's actually found where the water is coming from. Walk us through that situation.

Dave

Yeah, it's a really common call we get. The moisture meter tells you water is there, but it can't tell you where it started. So you've got evidence of a problem without a source, and that's exactly where acoustic detection earns its keep.

George

So what's actually happening when you put a ground microphone on a floor? What is it picking up?

Dave

A ground microphone picks up the sound of water escaping under pressure from a pipe. When a supply pipe has a leak, that pressurised water forces its way out through a crack or a joint failure, and it creates a very specific acoustic signature as it does. It's not a dramatic noise at all, it's a low-frequency hiss or a rhythmic pulse, depending on the pipe material and the ground conditions above it.

George

And that sound travels up through a solid floor?

Dave

It does. Concrete and screed actually conduct those low frequencies quite well. The ground microphone sensor sits directly on the floor surface, and the amplifier lets the engineer hear what's happening beneath. We'll typically work a grid pattern across the area the moisture meter flagged, listening at regular intervals and comparing the signal strength at each point.

George

So the two pieces of kit are working together, the moisture meter narrows down the zone and the ground microphone finds the point within it?

Dave

Exactly right. Moisture mapping gives ADI engineers the search area. Ground microphone technology then pinpoints the leak position within that area, sometimes to within a few centimetres. Without the moisture survey first, you'd be listening across the entire floor, which takes far longer. The two methods used together cut investigation time significantly.

George

What about pipes that aren't under pressure, waste pipes, for example? Does acoustic work there too?

Dave

Ground microphone technology works best on pressurised supply pipes, because the pressure is what drives that acoustic signal. A gravity waste pipe that's cracked won't produce the same sound. For those situations ADI would typically look at tracer gas or thermal imaging instead, depending on where the pipe runs and what access we have.

George

That makes sense. What about noise interference, a busy road outside, a boiler firing? Does that mask the signal?

Dave

It can make it harder, yeah. Background vibration from traffic does compete with the leak signal, and that's why professional acoustic equipment filters specific frequency ranges. ADI engineers are also trained to recognise the difference between a genuine leak signature and interference, the leak signal tends to be consistent and it peaks directly above the pipe, whereas general background noise stays flat across the whole floor.

George

So the pattern of readings across the grid is as important as any single reading?

Dave

Absolutely. You're looking for that peak, and it should form a clear hotspot. If the signal is roughly equal everywhere, that tells you something too, it might mean the leak is actually further away than the moisture pattern suggested, and the water has been travelling laterally through the substrate before soaking upward.

George

That's a good point, the wet patch isn't always directly above the leak.

Dave

Right, and that trips a lot of people up. Water follows the path of least resistance, so it'll track along a sand and cement screed, or along a pipe duct, before it surfaces. A moisture meter reading at one end of a room doesn't mean the leak is there. Acoustic detection traces the pipe route itself, which is why the two methods complement each other rather than one replacing the other.

George

Dave, that's really clear, thank you. So for any homeowners sitting with a report saying their moisture readings are elevated but no one's found the source yet, get in touch with ADI. ADI Leak Detection are among the UK's foremost residential leak detection specialists, and acoustic surveys are very much part of what they do.

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. More about how the podcast is made.