Each day, billions of gallons of water are lost worldwide to various factors, including leaks, water main failures, theft and metering inaccuracies. Not only does this represent the waste of a precious resource that many people do not have reliable access to, it also represents a massive amount of lost revenue for the utilities that provide water services.
In developed nations, Non-Revenue Water (NRW) is typically lower than in the developing world. In terms of an ideal NRW percentage, utilities should be aiming for 5 percent NRW or less – the 5 percent would consist of unbilled authorized consumption, which will be discussed later.
In North America, utilities typically have NRW levels ranging from 10 to 40 percent. In some developing nations, NRW has been recorded as high as 60 percent.
The fact that the NRW ranges are so wide is related to one of the major problems associated with NRW – the unknown. Without an active water loss control program, many utilities are unaware of what their actual NRW percentage is. Not knowing NRW or where the losses are coming from makes it difficult to develop proactive strategies to reduce losses.
On the financial side, 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 in cash would be generated and an additional 90 million people could have access to water.
NRW by definition
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 or hospitals.
Here are the primary causes of Non-Revenue Water explained in further detail:
Physical (or real) losses – leakage from all parts of the system
- Poor operations and maintenance
- Lack of active leakage control
- Poor quality of underground assets
Commercial (or apparent) losses
- Customer meter under-registration
- Data handling errors
- Theft of water in various forms (e.g. illegal connections)
Unbilled authorized consumption
- Water used by the utility for operational purposes
- Water used for fighting fires
- Water provided for free to certain consumer groups
Solutions for NRW reduction
To reduce NRW, utilities can use a variety of techniques that target different aspects of a water network.
Using correlators for small-diameter leak detection on pipes 300 millimeters (12 inches) and below is a very effective strategy for this size of pipe. Utilities often encounter the highest number of leaks on their small-diameter pipelines; however, these pipes are operating at a lower pressure and capacity than transmission mains, which reduces the amount of water lost per leak.
Focusing leak detection efforts on large-diameter pipes (12 inches and above) often provides utilities a very high return on investment. Leaks on trunk mains account for the majority of water lost from leaks, since the mains operate at high pressure and transport a large volume of water. Inline leak detection is the most effective method of identifying leaks on transmission mains, since the leak detection sensor passes the source of the leak and can provide close location accuracy.
A system wide leakage reduction approach can also be used to reduce water loss. By identifying metering inaccuracies and billing issues, utilities can reduce their water loss significantly. Typically, utilities with low NRW combine these efforts to control their water loss and reduce lost revenue.