Guide
What is a DMA (District Metered Area), and how is it set up?
Auditing a city network as a single whole is hard. A DMA (District Metered Area) divides the network into small, permanent parts whose inflow and outflow can be counted. Loss can only be managed where it can be measured.
What does a DMA solve?
A city-wide NRW figure such as "35%" is a number, but it does not say where the loss is. When the network is split into 15–20 DMAs, each zone's own minimum night flow is monitored; the loss narrows to a few zones and the field crew is sent to the right place.
The size of a DMA
Typically 500–3,000 connections or a few kilometres of main. In a DMA that is too large, small leaks disappear inside the night flow; one that is too small brings excess valve and meter cost. Size is set with regard to topography, pressure zones and natural boundaries (a stream, a main road, a railway).
Setup steps
1. Boundary design
Zone boundaries are drawn on the network map. Every connection on the boundary is either closed permanently or converted to a metered inlet. The aim: every drop entering the zone passes through a meter.
2. Boundary valve test
The valves that must be closed are shut one by one and checked for tightness. A single boundary valve that does not seal ruins the whole measurement.
3. Inlet meter / flow meter installation
A permanent electromagnetic meter or a temporary ultrasonic flow meter is fitted at the zone inlet; flow is logged in 15-minute steps.
4. Minimum night flow (MNF) measurement
From the minimum flow measured between 03:00 and 05:00, legitimate night use (cistern refills, industry, non-leak consumption) is subtracted. What remains is the physical loss flow. In Turkey, roughly 70% of the minimum night flow is physical loss.
Step testing — bringing the loss down to individual mains
The valves inside the DMA are closed in sequence through the night, starting from the far end. If the inlet flow drops noticeably when a valve is closed, the loss is concentrated on the main that valve feeds. The measurement area then narrows to a few hundred metres and the acoustic survey is targeted.
Permanent monitoring
A DMA is not a one-off. As the inlet meter logs continuously, the night flow rises within a few days when a new leak forms and the system gives early warning. The LeakExpert platform tracks that curve zone by zone.
- Related service: DMA, step & zero-pressure testing
- Measurement side: Flow measurement & NRW analysis
- Roadmap: Roadmap for cutting water loss
Also in the guide
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