Non-Revenue Water (NRW) can be defined as water that is produced for consumption and lost before it reaches the customer. The amount of NRW is typically represented as a percentage, and is made up of both real and apparent losses, as well as unbilled authorized consumption. Real losses refer to water lost from leaks and water main failures, while apparent losses come from theft and metering inaccuracies. Unbilled authorized consumption comes from water that is provided for public services that is not billed, such as fire hydrants.
The World Bank estimates that NRW costs utilities worldwide about US$14 billion annually. By reducing these losses by half in areas with the highest NRW, it is estimated that US$2.9 billion cash would be generated and an additional 90 million people could have access to water.
Utilities that run successful NRW-reduction programs often see an increase in revenue and improved service reliability. These utilities also gain a better understanding of their water system which allows for more effective water management in the long-term.
In terms of reducing NRW, locating leaks on large-diameter transmission mains represents the best opportunity for improvement. Leaks on small-diameter distribution mains are the most common, but the volume of water lost from these leaks represents a much smaller percentage of NRW than leaks on large-diameter pipes. Focusing leak and theft detection on transmission mains is the first step in a NRW-reduction strategy.
|System Input Volume||Authorised Consumption||Billed Authorised Consumption||Consumption (including water)||Revenue Water|
|Billed unmetered consumption|
|Unbilled Authorised Consumption||Unbilled metered consumption||Non Revenue Water (NRW)|
|Unbilled unmetered consumption|
|Water Losses||Apparent Losses||Unauthorised consumption|
|Customer metering inaccuracies|
|Real Losses||Transmission and / or distribution mains|
|Leackage and overflows at utilitiy's storage tanks|
|Leakage on service connections up to point|