How to tell if there is a water leak: 8 signs in a network

1. Rising minimum night flow

The flow measured at the reservoir outlet of a zone (DMA) drops to its lowest level between 03:00 and 05:00, when demand has stopped. If this minimum night flow rises over time while population and connection count stay constant, the difference is most likely a new physical leak. This is the earliest and most objective signal in network monitoring.

2. A local pressure drop

If the pressure at the far end of a main falls gradually while pump flow is unchanged, water is leaving the system somewhere in between. A 24/7 pressure logger record shows that drop at hourly resolution.

3. A widening gap between water produced and water billed

The difference between the total water entering the reservoir and the water billed to customers is the non-revenue water (NRW) share. If that share is above 30% and climbing, a measurable loss has built up in the network.

4. A flow sound at one point that never stops

A continuous hiss heard even at night next to a valve, a fire hydrant or a service connection is the classic leak sound. Acoustic listening amplifies it with a ground microphone and locates it between two points with a correlator.

5. Ground that stays wet in dry weather, or a strip of greener grass

Edge subsidence in asphalt, moss on a pavement, soil that stays wet without rain, or a strip of grass noticeably greener than its surroundings — all are signs of a leak that has reached the surface.

6. More frequent repairs

Pipe bursts that recur at short intervals in the same area are usually linked to high or fluctuating pressure. Repairs made without introducing pressure management move the problem to a neighbouring point a few months later.

7. An unexplained rise in chlorination and pumping costs

Every cubic metre of leaking water has been treated, chlorinated and pumped. If energy and chemical consumption rise without population growth, the difference is water seeping from the network.

8. Reservoir level falling at night too

The reservoir level should stabilise once demand stops. If it keeps falling through the night, a serious leak should be sought on the transmission main between the reservoir and the first metering point.

The signs are there — now confirm the location

These signs show that a loss exists, not where it is. Locating it requires systematic field work: zoning (DMA), night-flow measurement, step testing and acoustic surveying. LeakExpert runs this cycle as a single programme and reports every point with its coordinates.

• Method detail: Services
• Field examples: Projects
• Common questions: FAQ