Non-revenue water (NRW)

Non-revenue water (NRW), in Spanish 'agua no facturada (ANF)', is the volume of water that enters a city's or an industry's distribution system but generates no revenue, because it is physically lost, not measured correctly or not billed.

Components, according to the International Water Association

1. Real (physical) losses: leaks in pipes, bursts, tank overflows and faulty connections.
2. Apparent (commercial) losses: metering errors from deteriorated meters, fraud and consumption estimates.
3. Unbilled authorised consumption: park irrigation, fire hydrants and street cleaning that are used but not metered.

Key indicators

• NRW rate (%) = (Volume supplied − Volume billed) / Volume supplied.
• Real losses per connection per day: a standard benchmark used to compare utilities.
• Burst frequency = number of bursts per 100 km of pipe per year.
• Repair time: the time taken to fix a detected leak, which utilities aim to keep as short as possible.

Economic and environmental impact

• Every cubic metre of non-revenue water carries the cost of producing and treating water that is never sold.
• It also carries an embedded carbon footprint from the energy used to pump and treat it.
• At global scale, a widely cited study by Liemberger and Wyatt (2019) estimated worldwide NRW at around 126 billion cubic metres per year, with a conservative value of roughly US$39 billion per year.

A step-by-step approach to reducing NRW

1. Water balance audit: quantify losses following the water balance methodology of the IWA and AWWA.
2. District metering: divide the network into District Metered Areas (DMAs) with telemetry to localise losses.
3. Real-time monitoring: pressure and flow sensors and acoustic loggers.
4. Leak localisation: digital correlators, thermal imaging and fibre-optic sensing.
5. Pressure management: automatic pressure-reducing valves and hydraulic modelling (for example with EPANET).
6. Meter replacement: modern, accurate meters and remote-reading (smart) metering.
7. Awareness and fraud control: programmes to reduce illegal connections and tampering.
8. Performance-based contracts: arrangements in which the service provider is paid from a share of the savings achieved.

Emerging technologies

• Hydraulic digital twins: AI models that help anticipate leaks and optimise operations.
• Drones and remote sensing: to detect subsurface moisture along pipelines.
• Satellite monitoring: for large transmission mains.
• Digital traceability: to improve the integrity of metering data.

Co-benefits

• Resilience: lower abstraction reduces water stress in overexploited basins.
• Equity: more stable pressure and service in vulnerable neighbourhoods.
• Climate: lower carbon footprint and pumping energy.

Reducing non-revenue water is one of the most cost-effective actions to improve urban water sustainability, free up source capacity and cut emissions. With digital technologies, results-based finance and citizen engagement, utilities can bring NRW down substantially over time. At Manglai we help organisations measure their water-related impacts and prepare their sustainability reporting. Discover how Manglai can help you.