Does your utility track non-revenue water (NRW)? Non-revenue water is the term that replaces what was formerly called water loss reporting.

Graphic courtesy of Tata & Howard –

What is non-revenue water?

Non-revenue water is defined as your total system input volume (either water produced or purchased) less billed consumption.

From the chart below you can see that your system input volume falls into one of two categories – authorized consumption or water losses. Each of these are then further divided into two sub-categories – authorized consumption into billed and unbilled authorized consumption and water losses into apparent and real losses.

Non- revenue water is the total of unbilled authorized consumption, apparent losses, and real losses.

Let’s analyze each of these in more detail:

Billed authorized consumption

This is pretty straightforward – this is what your utility is in business to do! Billed authorized consumption can be either metered or unmetered, but it is accounted for and you (hopefully) get paid for it!

Unbilled authorized consumption

Unbilled authorized consumption can also be either metered or unmetered. Unbilled metered consumption would include your own facilities if you don’t bill yourself. Examples of unbilled unmetered consumption would be flushing lines or the fire department drawing water from hydrants in your system.

Apparent losses

Apparent losses are also broken down into two types – unauthorized consumption and customer meter inaccuracies and data handling errors. Unauthorized consumption is self-explanatory – it’s stolen water or any other consumption without the utility’s authorization.

Customer meter inaccuracies includes meters slowing down over time due to wear and tear. Remember, meters are like people – they slow down, not speed up, as they get older! Metering inaccuracies could also be due to failing to install a compound meter for a multi-unit apartment building and not registering low flows during off-peak times.

Data handling errors would encompass such things as meters that are billed using the wrong billing units. For example, if a meter is read in thousands of gallons but billed in hundreds of gallons, the apparent loss is a factor of 10.

Real losses

Real losses are further defined as leakage in transmission and distribution mains, leaks and overflows from storage tanks, and service connection leaks up to the meter.

Leaks in transmission, distribution, and service lines are what first comes to mind for most people when they think of water loss, but leaks and overflows from storage tanks must also be considered.

AWWA resources

The American Water Works Association (AWWA) offers free water audit software to assist with accounting for non-revenue water. They also offer a concise, two page document describing best practices and terminology to help explain the process.