Water a utility puts into its pipes but never bills for — leaks and bursts, plus meter under-registration, theft and unbilled authorised use.
🤖 This definition was generated with AI from the sources linked throughout. It has not had a complete human review — treat it as a starting point and follow the sources. How this works.
Non-revenue water (NRW) is the gap between the water a utility pushes into its network and the water it actually gets paid for. The International Water Association splits that gap three ways: real losses — leaks, bursts and overflows; apparent losses — meters under-registering, theft and billing errors; and unbilled authorised use, such as mains flushing and fire-fighting. Only the first is a hole in a pipe. The other two are holes in the paperwork.
It is the single number that makes water telemetry worth buying, because it turns sensors into money. Istanbul's İSKİ carved its network into district metered areas and watched night-flow through SCADA from 2008, reporting NRW down from 22.3% in 2019 to 18.6% by 2024. Casablanca went sensor-first, with roughly 4,000 fixed acoustic listeners across a fully sectorised 7,000 km network, finding leaks before they surface. Both figures are the operators' own.
Treat the percentage with care. It moves whenever total input moves, so a wet year can improve it without a single pipe being fixed, which is why the IWA prefers litres per connection per day. A falling figure can also mean better meters rather than fewer leaks. And instrumentation alone does not shift it: Montreal fitted about 19,500 non-residential buildings with remote-read meters, and the city's own data still put overconsumption and losses at 30%, the same as in 2015.
Added 2026-08-01 · Part of the growing Smart City Glossary