The different types of leakage in the water distribution network each have different impact and a different economic cost to remedy. The overall run-time of leaks consists of awareness, location and repair times (see opposite).
Long leakage run-times generate large water losses, even from relatively small leaks.
The four basic methods for managing real losses are:
1) Pressure management – reducing excess pressure, reduces the volume of water lost through leaks (including customer-side leaks which are estimated to account for around 25% of overall leakage). Lowering or stabilising pressure also helps to reduce bursts by putting less ‘strain’ on the infrastructure.
2) Active Leakage Control – the process of proactively looking for un-reported leaks and bursts, this consists of two distinct stages:
- Leak monitoring and localisation.
- Leak location and pinpointing.
3) Speed and quality of repairs – a rapid & efficient response to reported leaks that sends teams to the correct location.
4) Pipe material selection, installation, maintenance, renewal and replacement – asset renewal to reduce the rate of occurrence of new leaks, and investment in facilities such as district meter areas (DMAs) and telemetry to improve the efficiency of Active Leakage Control operations.
The combined action of these four control strategies is sometimes known as ‘squeezing the box’ (see opposite) because they focus on reducing the rate of leakage towards a ‘Sustainable Economic Level of Leakage’. This is defined as the level at which fixing a leak is less than the cost of not fixing the leak – which includes environmental damage and the cost of developing new water resources to compensate for the water lost through leaks.
The use of telemetry to monitor the network helps determine that level and is essential to implementing these water leakage reduction strategies.
How does telemetry help?
It greatly helps with the formation of district metered areas (DMAs) which make it possible to divide the water distribution network into small, isolated, and independent water distribution networks. Within the DMA the quantities of water entering and leaving the area are controlled using the closure of metered valves, the values are reported and the valves are controlled with telemetry and SCADA systems.
A permanently monitored DMA is the most effective tool to help reduce the duration of unreported leakage. Monitoring night flows is used to identify unreported leaks, and provides data required to efficiently locate them.
Telemetry is also used to manage water pressure using valve and pump controls. Small reductions in average and maximum pressures over large areas are usually more beneficial in reducing burst rates, on both mains and services, than large pressure reductions over small areas.