Correlation & Data Logging

What It Is

Correlation is a mathematical technique for locating a leak using two or more acoustic sensors placed at known points along a pipe. The leak emits sound that travels in both directions; the time difference between the sensors picking up the signal tells the system exactly where the leak is, with sub-metre precision.

Data logging is the complementary technique. We install small electronic sensors that record water pressure, flow, or temperature continuously for 24–72 hours, then retrieve the device and analyse the trace for the patterns that reveal an intermittent leak.

How It Works

For correlation, the technician places two acoustic sensors at the meter, an isolation valve, or any other accessible point along the line. The system records both signals in sync, calculates the time-of-arrival difference, and converts it (using the known signal velocity in that pipe material) into a distance from each sensor.

For data logging, the technician installs a small unit at a known reference point and leaves it in place. When retrieved, the recorded trace is exported and read against typical-use baselines. A genuine leak shows up as a sustained low-flow signature during periods when no fixture is in use — an unmistakable pattern that is invisible during a single inspection visit.

What It Detects Best

Correlation is the technique of choice for large properties, commercial buildings, and any pipe run too long for a one-pass acoustic walk. The mathematical precision is unaffected by run length — the only requirement is two accessible sensor points.

Data logging is the right tool for intermittent leaks, very small leaks on commercial flow meters, and any case where the symptoms come and go on a schedule that does not match the inspection window.

When We Use It

We deploy correlation on commercial sites, multi-unit residences, large rural blocks, and any job where the pipe layout is too long or too complex for a single acoustic sweep.

Data logging is reserved for the cases where every other technique has come up clean but the symptoms persist — high water bills with no detectable leak on inspection day, intermittent damp patches, or strata water-meter discrepancies that no one can explain.

What The Client Experiences

Correlation is a single-visit job, similar in feel to a long acoustic survey. The technician sets up the sensors, runs the recording, and analyses the trace on site.

Data logging is a two-visit job. We install the device on the first visit (typically 30 minutes) and return 1–3 days later to retrieve it and review the trace with you. The device itself is small, silent, and unobtrusive — most clients forget it is even there.

Why It Matters

Correlation is what makes precise detection feasible at commercial scale. Without it, a 200-metre supply line is a 200-metre acoustic walk; with it, the same line is a single-pass calculation that takes 20 minutes.

Data logging is what makes intermittent leaks solvable. A leak that only runs at 3am for 90 seconds will never be caught on a daytime inspection — but it will show up unmissably on a 72-hour trace. For the small but stubborn class of jobs where this is the only way home, data logging is the answer.