Non-revenue water, or NRW, is a major problem for utilities around the world. It is water that has been expensively and carbon-intensively sourced, treated and pumped, but which no-one ever pays for because it goes missing from pipeline networks. Most NRW is due to leakage, but there are other types.

A big issue with non-revenue water is that no-one really knows how much of it there is. A lot of utilities do not record it. However, experts have estimated that as much as 30% of the world’s precious water is lost to NRW, and in some countries it is much higher.

At levels like this, against a background of climate change and increasing water scarcity, non-revenue water is an issue for the environment, society and the financial viability of water producers themselves.

In this blog we take a look at the different types of non-revenue water and the traditional and emerging solutions which are available to measure and prevent it or, at least, limit its impact.

Non-revenue water explained

Non-revenue water is water that has been taken from the environment, treated, put into a network of distribution pipes and ‘lost’ before it reaches a paying customer. But not all NRW is the same. The International Water Association (IWA) has defined three main types as well as a set of standard terms which are recognised in most parts of the world.

  • Real (or physical) water loss
    The biggest cause of NRW is leakage. Leaks are ‘lost’ water in the true sense of the word; water which has escaped from the system and never gets used by anybody. That is why, in NRW language, leakage is often referred to as a ‘real loss’.


  • Apparent (or commercial) water loss
    Unlike leakage, some non-revenue water reaches its final destination and gets used but it is not paid for. This might be because of theft or inaccurate metering. This NRW is called an ‘apparent loss’. It appears to go missing, but in fact it’s still there.


  • Unbilled authorised water consumption
    Sometimes water is used legally but it cannot be billed. Water the utility company uses itself for essential pipe cleaning fits into this category, as does water drawn off for firefighting. This is usually only a small component of total NRW.


Each type of non-revenue water needs different solutions to prevent or control it. But whatever the reason, a high level of NRW is increasingly seen as a waste of resource with environmental and societal impacts.

The result being that considerably more water is removed from the environment than society uses, with all the associated waste in chemical and pumping costs. In places where water is scarce and electricity is generated from fossil fuels this can have major implications for both water resilience and decarbonisation.

Non-revenue water is also a big deal for water utility staff and consumers. If a large proportion of water being produced by a utility is NRW, it can be harder to match production to consumer demand, especially in dry spells.

Plus, it is a cost which is not recouped through bills, making it harder to keep water tariffs at a reasonable and affordable level. These financial and reputational risks can have implications for investment and, in extreme circumstances, can even lead to regulatory action.

On the other hand, managing NRW well can improve financial performance, help make cities more livable, mitigate and adapt to climate change and reduce energy consumption.

What is the difference between non-revenue water and unaccounted-for water (UFW)?

Non-revenue water is the contemporary term for any water which is put into a public pipeline network which is not paid for by consumers. This can include water that leaks from the system, is stolen or used without being billed, amongst other things.

Unaccounted-for water (UFW) is an older term, defined as the difference between total production and total consumption and is usually expressed as a percentage of system input percentage (SIV).

Many water loss policy experts now consider it too imprecise and in 2003, the AWWA Water Loss Control Committee recommended stop using UfW as an indicator, or expressing it as a percentage.

Solving water loss, the FIDO way.

Causes of non-revenue water

There are lots of reasons why NRW happens. Leakage is particularly tricky for water utilities because the vast majority of it – around 90% – never shows above ground, making it costly and time-consuming to fix. It’s not necessarily because of the age of the pipe, although this can be an factor. Other causes include corrosion, poor installation, joint or fixture failure, damage, ground movement and pressure surges.

Theft is one example of non-revenue water. Theft can range from individuals tapping into pipes illegally to get free water or unscrupulous commercial customers tampering with bypass vales on fire mains to avoid their usage being metered all the way to large-scale operations where stolen water is sold on the black market. Hydrant abuse is similar problem.

It’s where water hydrants get opened deliberately for recreation or to create a nuisance. Although not strictly speaking theft, hydrant abuse is a known problem in some urban areas, especially in hot weather.

Other NRW comes from within the utility itself. Meters that are not properly calibrated or maintained correctly may fail to record all usage accurately or may even overstate usage – leading utilities to bill customers incorrectly or lose out on revenue due to undercharging. Human error can also cause problems, whether that’s inaccuracy in meter readings, billing errors or poor data management generally.

Finally, there’s authorised unbilled consumption. This includes water used by the utility’s staff for operational tasks such as flushing mains and cleaning vehicles as well as for water legally drawn off and by fire services. Because it is not paid for, it can be poorly managed, but it is rarely a significant proportion of total NRW.

Also read:
United Utilities: FIDO halves leak run time for United Utilities

Solutions to combat non-revenue water

The first step towards reducing non-revenue water is to understand the scale of the problem. An annual water balance, or audit, is a good place to start. The IWA Water Balance is considered the best practice standard and many regions offer free versions adapted to local circumstances, like the AWWA’s Water Audit Software in the US.

Audits involve collecting records or estimates of water supply, customer usage, authorised unbilled unmetered water volumes, meter testing and/or calibration over the space of a year.

Once a utility understands how much of each type of non-revenue water it needs to manage, it can set targets based on a cost-benefit assessment of forecast expenditure versus potential savings and revenue increases.

Interventions should then be targeted at measurable performance indicators such as part of an active leakage control (ALC) policy. ALC could include enhanced maintenance programmes and improved operational and data-handling processes to minimise water loss, such as managing pressures to reduce the amount of water escaping, as well as leak detection and repair.

Many utilities only respond reactively to leaks, usually when a customer reports a burst or loss of water at the tap. But a programme of active leak control combining pressure management and leak detection with prioritised repair using dedicated resource can be very effective.

ALC is more cost effective than replacing a section of pipe completely. However, where pipes leak frequently and are subject to multiple risk factors like age, ground movement, defects, or a high-profile location, pipe replacement could be the only acceptable option.

Solving water loss, the FIDO way.

Technologies for reducing non-revenue water loss

Correctly calibrated equipment like meters and sensors help utilities identify where water is being lost before it affects customers. Without them, spotting NRW is much harder. Manual tools and techniques like listening sticks and step-testing are time-consuming and take a lot of resource.

Acoustics remains the background of most leak detection technology and digital tools based on leak ‘listening’ have evolved to make the process more efficient. Acoustic loggers attached to the network send alarms when a noise reaches a set threshold, so that analysts can do the listening in the office.

In-field devices like ground microphones do the job of listening sticks but without the limits of human hearing, and correlators can help pinpoint leaks on the ground.

While a great step forward in leak detection, acoustic technologies bring their own drawbacks. They can generate large amounts of data which still needs manual processing. To limit the amount of data to manageable levels, some utilities set the logger thresholds too high, meaning that many leaks, particularly the larger ones which make less noise, are missed.

The availability of digital sensor and metering data via IoT means advanced technologies incorporating AI can now use smart data analytics to provide rapid actionable insight into the performance of water networks.

As well as helping managers make best use of limited resource by eliminating false positives and wasted effort, the analysis of data at real-time and at scale speeds up response times and cuts leak run times.

Some innovative technologies have introduced previously-unavailable levels of NRW insight. For instance, FIDO AI, which was trained only on verified leak data, has the unique ability to gauge leak size from sensor data, giving utilities the power to prioritise the most serious leaks, the largest leaks, and save more water faster.

How FIDO Tech combats non-Revenue water and reduces water loss

FIDO helps clients improve financial returns and meet regulatory targets using actionable AI-led data insight at multiple points in the leakage value chain: from leak identification, prioritisation and location to evidenced performance reporting and revenue assurance. The only thing we don’t do is repair pipes.

Our AI has the unique distinction of being able to identify leaks and, most importantly, rank them by size, even in the noisiest networks, and regardless of pipe material or condition.

This single piece of actionable insight on leak size sets us apart. It enables us to prioritise repairs, reducing leak runtime and maximising water loss reduction.

FIDO AI treat leaks as assets, tracking and learning from them on an endless verified feedback loop getting more and more accurate all the time: currently over 92%. We flag the large leaks as a priority, locate them exactly and then verify the effectiveness of the utility’s own repairs.

Finally, we leave our free sensors in place for continual network monitoring. Even small leaks are on our radar. FIDO AI tracks them until they degrade or aggregate to a point they become economic to repair.

Being consciously sensor-agnostic, FIDO AI can automatically upload and analyse acoustic or kinetic data from any other proprietary device, immediately improving return on previous investment.

But we don’t need existing data. Small HD FIDO sensors, called FIDO Bugs, are supplied as part of the service and are among the most sophisticated on the market. This means any network can immediately match the level of the best irrespective of its current level of digital maturity.

FIDO Bugs don’t have thresholds, and FIDO AI has no limits on the amount of real-time data it can interpret, so no no leak noise is missed. The other advantage of Bugs is that FIDO is constantly enhancing their functionality in response to client needs. For instance, Bugs can also be used as correlators and ground microphones and will soon be able to detect certain pipe tampering.

Complete leak detection with FIDO Direct

Through our FIDO Direct service, we offer an end-to-end leak detection and monitoring service inclusive of sensors and manpower. We deliver all the in-field actions and improved operational processes needed to meet pre-agreed reduction targets. All the utility commits to is fixing the leaks FIDO finds.

FIDO Direct has already seen multiple successes across the UK. We partnered with Northumbrian Water to reduce leakage by 37% across 15 assigned district metering areas (DMAs). We are also working with Microsoft and Thames Water on a first-of-a-kind collaboration to address water leakage in London’s public water network.

Also read:
Microsoft and FIDO Tech launch collaboration to drive down water losses

More about FIDO Direct

FIDO Direct is a complete package, designed to deliver against guaranteed pre-agreed leakage reduction targets. It works because we take full responsibility for leakage reduction using our optimised AI-driven detection process.

It is an end-to-end service solution providing all hardware, software and boots on the ground delivering the blue line, for you to simply dig and repair.

First, FIDO experts deploy FIDO AI using FIDO equipment. Then, we identify leakage across a defined area with unerring accuracy, promoting leaks ranked by size and location for repair which hit your pre-agreed target. Finally, through the power of FIDO AI, we validate the repair to produce an end of project validation report.

For more information on any of FIDO’s solutions contact us today.