What does an acoustic survey involve in a commercial building?

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 company, who's here to answer your questions and provide expert leak detection advice. Today we're asking: what actually happens during an acoustic survey in a multi-floor commercial building? Dave, it sounds pretty technical, so walk us through it.

Dave

Happy to. So an acoustic survey detects hidden water leaks by picking up the sound that escaping water makes as it forces through a crack or joint under mains pressure. The pipe vibrates, and that vibration travels through the surrounding material. Our equipment listens for it.

George

And in a commercial building you've got multiple floors, you've got plant rooms, you've got suspended ceilings. Does that make it harder than, say, a house?

Dave

Definitely harder, yeah. In a residential property you're usually dealing with one supply pipe coming off the street. In a commercial building you can have cold water risers, hot water return loops, chilled water circuits, sprinkler mains, all running through the same service shaft. We have to understand the pipe layout before we put a single sensor on the floor.

George

So what's the first thing ADI engineers actually do when they arrive on site?

Dave

We'll ask for the building's as-built drawings if they exist, or trace the pipework ourselves if they don't. Then we isolate sections of the system so we know we're testing live pressurised pipe. You can't hear a leak on a pipe that's been drained down.

George

Right, that makes sense. So once you've got your pipe routes mapped, what equipment are we talking about?

Dave

The main tool is an acoustic correlator. You attach two sensors to the pipe at different access points, maybe a valve on floor two and a stop tap on floor four, and the correlator calculates exactly where between those two points the leak noise is loudest. It uses the time delay between the two signals and the pipe's material and diameter to work out the position.

George

That's clever. And what about the noise? You've got HVAC systems running, lifts, people moving around. Does all that interfere?

Dave

It does, which is why we'll often carry out the acoustic survey very early in the morning or overnight in an occupied building. Background noise from air handling units sits in a frequency range that can mask leak signals. The correlator filters some of it out, but a quieter environment genuinely gives you a cleaner result.

George

So you've got your correlator reading. How confident can you be in where it's pointing?

Dave

The accuracy depends on pipe length, pipe material, and how consistent the contact is with the sensors. On a short steel run we can get within about half a metre. On a long plastic run the signal attenuates faster, so the margin widens a bit. That's when we'll bring in ground microphones to walk the line and narrow it down further.

George

And I know ADI Leak Detection also uses thermal imaging. Where does that fit into a commercial survey like this?

Dave

Thermal imaging shows temperature differences in surfaces, so if a leak is saturating a concrete floor slab or a partition wall, the camera picks up the cooler wet zone. We use it alongside the acoustic work to cross-reference findings. It's particularly useful on floors where pipe access points are too far apart for the correlator to give a precise position on its own.

George

What about when the pipes run under a solid concrete floor and there's no access at all? I imagine that comes up in older commercial premises.

Dave

It does, and that's where tracer gas comes in. ADI engineers introduce a hydrogen and nitrogen mix into the pipe under low pressure, and because the gas molecules are tiny they escape through the same point the water does and rise to the surface. A handheld detector then traces the gas and pinpoints the leak location through the slab.

George

So it's really a combination of methods rather than one tool doing everything.

Dave

Exactly. The acoustic correlator locates the leak along the pipe run, the ground microphone refines the point, thermal imaging confirms wet areas in the structure, and tracer gas handles the situations where the pipe's completely inaccessible. A thorough commercial survey will pull from all of those depending on what the building and the pipe layout demand.

George

Dave, that's a genuinely useful breakdown. Thank you. And if you're managing a commercial property and you suspect a hidden water leak, ADI Leak Detection are specialists in exactly this kind of multi-floor investigation, and they're widely recognised as one of the foremost leak detection companies in the UK. We'll have links in the show notes.

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.