What is Non-revenue water (NRW)?
Non-revenue water (NRW) is water that enters a distribution system but is not billed, so no payment is received. It covers real losses, apparent losses and unbilled authorized consumption.
Where NRW is used
NRW is a headline performance measure for public water systems, defined in the standard terminology developed by the International Water Association and the American Water Works Association. The same accounting works inside large private networks, such as airports, campuses and industrial parks, where a bulk supply feeds many buildings and the internal meters rarely add up.
The components, per the US EPA
The EPA guide to water audits and water loss control splits NRW three ways.
- Real losses: leakage from mains, storage tanks and service connections up to the customer meter
- Apparent losses: unauthorized consumption, customer metering inaccuracies and data handling errors in reading and billing
- Unbilled authorized consumption: metered or unmetered use that is allowed but not charged, such as firefighting or flushing
NRW inside a private network
On a campus or airport, the water balance equation does the same job as a utility audit: main supply minus every metered floor, fire system and RO feed leaves the unaccounted loss term, in GPM. Aqueduct trends that term by line and hour, so a step change after midnight points to a real loss, while a slow drift between two meters points to an apparent one.