Leak detection and line balance
A leak is a flow that arrives somewhere it should not. Finding it is a matter of measuring the same water at two points and noticing that the numbers do not match.
Line balance method
Meter the inflow to a section and the outflow from it. On a sound section those match within instrument tolerance. A persistent difference is loss. The technique is simple; the difficulty is that on a large main the leak may be a small fraction of throughput, so the instrument needs to resolve a small difference reliably.
Two practical rules make this work. Use the same meter at both points sequentially rather than two different instruments, which cancels most systematic error. And measure during stable low demand, because comparing two points during a demand swing measures storage change, not loss.
Minimum night flow
On a distribution district, the flow that persists between 2 and 4 in the morning is mostly loss. Logging over several nights establishes a baseline, and a rising baseline across weeks means a growing leak. This is the standard technique in network leak management and it needs an instrument that logs unattended for long enough to see a trend, not a spot reading.
Where clamp-on measurement helps most
- Between existing permanent meters, where you suspect loss but the permanent metering is too sparse to localise it
- Bisecting a suspect section to halve the search area, then halving again
- Verifying a permanent meter that is reporting a loss which may be instrument error rather than a real leak
- Internal building leaks, where the incoming supply reads flow at 3 a.m. with every fixture closed
The limits
This is flow measurement, not acoustic leak location. It tells you a section is losing water and roughly how much. Pinpointing the leak to a specific joint still needs acoustic correlation or leak noise logging. Renting a flow meter narrows the search; it does not end it.