Why acoustic leak detection still does the heavy lifting
Satellites, smart meters and machine learning all have a place in a modern water loss programme. But when a utility actually needs to put a mark on the road and dig, the leak is almost always found the same way it was 40 years ago: by listening to it.
Acoustic leak detection remains the most reliable, lowest-cost way to locate non-visible leaks on pressurised water mains. The physics have not changed. What has changed is the equipment, the way it is deployed, and the number of brands competing for a place in a utility’s toolkit.
This guide walks through how acoustic leak detection works, the main technology categories, the brands you will see on tender submissions across Australia and New Zealand, and how to choose between them. It is written for the people who have to make those decisions: network engineers, asset managers, and the operations teams responsible for keeping water in the pipe.
If you are after the service rather than the theory, our acoustic leak detection for water networks page covers what we deliver and where.
How acoustic leak detection works
Water escaping a pressurised pipe through a hole or crack creates turbulence. That turbulence generates vibration and sound, which travels in three ways: along the pipe wall, through the water column, and outward into the surrounding soil. Acoustic leak detection equipment picks up one or more of those signals and uses them to narrow a leak’s position from kilometres down to a hand-span.
Four variables decide how easy that is in practice:
- Pipe material. Metallic pipes (cast iron, ductile iron, steel) carry leak noise well over long distances. Asbestos cement is middling. Plastics (PVC, PE) damp the signal badly, so noise travels a far shorter distance and sits at lower frequencies.
- Pressure. More pressure means more turbulence and a louder, higher-frequency leak. A leak at 60 metres of head is far easier to find than the same hole at 20 metres.
- Pipe diameter and soil. Large-diameter mains spread the noise over more wall area and more water, which is why trunk main leak detection needs its own toolkit. Wet clay and sandy soils absorb ground-borne noise; compacted road base transmits it.
- Background noise. Traffic, pumps, PRVs and customer use all compete with the leak. This is why so much acoustic work happens between midnight and 5 am.
Understanding those variables matters more than any single piece of equipment. Every technology below is a different trade-off between sensitivity, range, cost per kilometre and the skill required to interpret what it hears.
The main acoustic leak detection technologies
Most utilities end up using several of these in sequence: a wide-area tool to flag where leaks probably are, a correlator to narrow the search, and a ground microphone to confirm the dig point.
1. Listening sticks and ground microphones
The listening stick is the oldest tool in the kit and still one of the most useful. A technician places it on a valve, hydrant or meter and listens directly for leak noise through the fitting. The electronic ground microphone does the same job on the surface above the pipe, with amplification and filtering that let the operator hear through road base and concrete.
These are confirmation tools. They do not find leaks on their own across a 300 km network, but no active leak detection programme marks a dig without one.
2. Leak noise correlators
A correlator uses two or more sensors placed on fittings either side of a suspected leak. Each sensor hears the leak slightly out of time with the other. Knowing the distance between the sensors and the speed of sound in that pipe, the correlator calculates where the noise originates. On a metallic main in good conditions, that answer is accurate to within a metre or so.
Correlators are the workhorse for pinpointing on distribution mains and, with hydrophone sensors inserted into the water column, on large-diameter trunk mains. Our TM3 trunk main correlator case study shows the method finding something the client did not expect: an unauthorised connection rather than a leak.
3. Acoustic noise loggers
Noise loggers are small sensors deployed on fittings across a DMA, usually one every 100–300 m. They record the quietest sound level at each fitting overnight. A steady, low, consistent noise floor points to a leak; a noise that comes and goes is more likely customer use. The loggers are either collected by a technician driving past (lift-and-shift) or left in place permanently, reporting over cellular networks.
Loggers are a survey tool. They tell you which fittings deserve a visit, which is how a crew can cover far more of a network per shift than by sounding every valve. Pairing them with district metered areas and night flow data is what turns a pile of noise readings into a prioritised work list.
4. Correlating loggers
A correlating logger does both of the above. Each unit time-stamps its recording precisely enough that a pair of neighbouring loggers can correlate against each other and give a leak position overnight, before a technician has even arrived. Deployed permanently, this is the basis of real-time leak detection on a fixed network, where new leaks are flagged within days of appearing rather than at the next annual survey.
5. In-pipe acoustic inspection
For long trunk mains, outfalls and sewer rising mains, the most sensitive microphone is one travelling inside the pipe. Tethered tools are inserted through a single access point and pulled along by the flow, carrying a hydrophone (and often a camera) past every metre of pipe. Free-swimming tools go further still, released at one end and retrieved at the other, tracked from the surface as they go.
Because the sensor is in the water column, these tools hear leaks that are inaudible from the surface, including on plastic and large-diameter concrete mains where correlation struggles. The trade-off is logistics: insertion points, flow conditions and traffic management all need planning. Our inline pipeline inspection page and the top three trunk main leak detection methods article cover when each approach makes sense.
6. Permanent acoustic monitoring on critical mains
Some assets are too important to survey once a year. A permanently installed array of acoustic sensors along a critical trunk main, bridge crossing or pump station delivery main listens continuously and alerts the operator when a new noise signature appears. This is less about finding today’s leak and more about pipeline monitoring: catching the small leak before it becomes the burst that closes a highway.
The acoustic leak detection brands you will see in Australia and New Zealand
No single manufacturer covers every category well. Our field teams carry equipment from several of the brands below, chosen for the job rather than the badge, and we are brand-agnostic when advising clients on what to buy. What follows is a plain description of where each brand sits, not an endorsement.
| Brand | Origin | Best known for | Where it fits |
|---|---|---|---|
| Gutermann | Switzerland | ZONESCAN fixed and lift-and-shift correlating loggers; AQUASCAN and MULTISCAN correlators; EASYSCAN ground microphone | Permanent DMA monitoring and real-time leak detection; strong on correlation between loggers |
| Sewerin | Germany | SeCorr correlators; AQUAPHON ground microphones and listening equipment | Pinpointing and confirmation; widely carried by Australian field crews |
| HWM (Halma) | UK | PermaNET+ and Permalog noise loggers; MicroCorr correlators; Xmic ground microphone | Large-scale logger deployments; long history on UK and Australian networks |
| Ovarro (formerly Primayer) | UK | Enigma correlating loggers; Phocus correlators; Eureka ground microphones | Lift-and-shift and permanent correlating logger programmes |
| Echologics (Mueller) | Canada | LeakFinderST and EchoShore correlation; ePulse acoustic condition assessment | Trunk main correlation using hydrophones; the same acoustic approach is used to estimate pipe wall condition |
| Xylem (Pure Technologies) | Canada / US | Sahara tethered inspection; SmartBall free-swimming inspection | In-pipe acoustic leak and gas pocket detection on large-diameter transmission mains |
| Acquaint | Netherlands | Acquarius and Aquabrella inline inspection tools | In-pipe inspection combining acoustics with condition data on pressure pipelines |
| Fuji Tecom | Japan | FSB-8 and related listening equipment; LC-series correlators | Robust, simple confirmation tools |
| SebaKMT (Megger) | Germany | Correlux correlators; Sebalog noise loggers | Pinpointing and logger surveys |
| vonRoll hydro | Switzerland | ORTOMAT permanent loggers and ORTOMAT-MTC correlating network | Permanent acoustic networks on distribution systems |
A few observations from the field on how these groups differ.
Logger-led brands (Gutermann, HWM, Ovarro, vonRoll) compete on battery life, radio range, the quality of their correlation between neighbouring units and, increasingly, the software that turns thousands of nightly readings into a short list. Hardware is converging; the software and the cost per logger per year are where the real differences now sit.
Pinpointing-led brands (Sewerin, Fuji Tecom, SebaKMT) are judged on how well a technician can hear through them in a noisy street at 2 am. Filtering, headphone quality and sensor sensitivity on plastic pipe matter more than the brochure.
In-pipe brands (Xylem, Acquaint, Echologics) are sold as a service as often as a product, because the deployment is the hard part. Aqua Analytics’ own AquaSnake tethered tool and AquaSphere free-swimming device sit in this category, developed because our clients needed live inspection of long trunk mains without a shutdown and without the mobilisation cost of importing a tool and crew for every job.
How to choose the right acoustic leak detection technology
The wrong question is “which brand is best?”. The right one is “what is my network made of, how much is leakage costing me, and how often do I need to look?”. Five factors settle most decisions.
- Pipe material mix. A network that is 70% PVC and PE will get limited value from a standard logger survey and should budget for more ground-sounding and, on larger mains, in-pipe inspection. A predominantly cast iron and AC network is ideal correlator and logger territory.
- Leakage level and value. Run the numbers before the tender. Our Water Loss ROI Calculator and the Infrastructure Leakage Index explainer will tell you whether you are looking at a one-off sweep or a standing programme. Permanent loggers only pay back where leakage is high, water is expensive, or both.
- Survey frequency. If a full network sweep every 12–18 months is enough, a contracted lift-and-shift programme is usually the cheapest option per kilometre. If leaks need to be caught within days, a fixed network with cellular correlating loggers is the only option that does it.
- Critical assets. Trunk mains, river crossings and single-feed supplies justify a different tier of investment, usually a combination of in-pipe inspection on a cycle and permanent monitoring in between.
- In-house capability. Equipment is the easy part to buy. Owning a fleet of correlators without a team trained to use them nightly is one of the most common ways utilities waste leak detection budget. Be honest about whether the skill sits in-house or whether a specialist contractor will get more leaks per dollar.
Most councils and utilities we work with land on a hybrid: a contracted annual or biannual acoustic survey across the distribution network, loggers left permanently in the two or three DMAs that misbehave most, and a trunk main programme on its own cycle.
The part no brand can sell you: the technician
Every brand on the list above will show you a demonstration leak found to the centimetre. What the demonstration cannot show is the plastic service line under a busy arterial road, the PRV chattering two blocks away, or the correlation that says 47 metres when the valve spacing on the plan is wrong by ten.
Acoustic leak detection is an interpretive skill. The equipment produces a signal; a person decides whether it is a leak, a customer running a tap, a pump, or nothing at all. That judgement is built over years of nights on the road, and it is the reason two crews with identical kit can return very different find rates from the same DMA.
At Aqua Analytics we call this the Human Layer. Our investment in technology is matched by our investment in the people who use it: structured training, mentoring from technicians with decades on the tools, and a career pathway that keeps experienced people in the field rather than losing them to the next job. If you would rather build that capability than buy it, we are always looking for people who want to learn the trade properly.
Where to from here
Acoustic leak detection is not one technology but a family of them, and the brands behind each are mature, competitive and broadly comparable on hardware. The decisions that actually move a utility’s leakage figure are about matching the tool to the pipe, setting a survey cycle the budget can sustain, and putting skilled people behind the equipment.
If you are scoping a leak detection programme, reviewing a logger tender, or trying to work out why last year’s survey found less than expected, talk to our team. We work across Australia and New Zealand and will give you a straight answer on what the network needs, whichever brand ends up on the truck.
Read more about our acoustic leak detection services for water networks.
