Does a quarter of our water really disappear?

1.The myth: “a quarter of the water simply disappears”

You often hear that more than a quarter of the water fed into a utility's mains and distribution network “disappears” before it ever reaches consumers. In Hungary, that would mean 160–170 million cubic metres vanishing out of 650 million cubic metres.

The figure itself is correct – in Europe the volume concerned really does tend to be around a quarter of the system input volume – but the picture behind it is often misread: the water does not literally disappear, nor is it necessarily wasted. The essential point is that it is not billed.

Getting these concepts right matters, so that everyone can understand the work water utility professionals do and the service they provide.

2.What exactly is Non-Revenue Water?

The industry uses the term Non-Revenue Water (NRW) for the volume of water that is fed into the network – the system input volume – but generates no billing revenue. It is made up of two fundamentally different components, real (physical) losses and apparent (commercial) losses, and only the first of these is water that has genuinely escaped or leaked away.

Both real and apparent losses have several components; the two key distinctions are authorised and unauthorised use.

Authorised consumption includes water used for firefighting, mains flushing during maintenance, and certain public-purpose uses. This water genuinely serves a purpose; it is simply that not all of it, and not in every case, has an invoice attached to it – so it is certainly not water that has “disappeared”. Unauthorised consumption also reaches the consumer, but in this case the consumer is actively trying to avoid being billed.

Metering inaccuracy, likewise, is not simply a matter of meters being obsolete or unsuitable. It reflects the plain fact that every measurement carries a margin of error. Reducing that error is precisely why, in Hungary, water meters must be replaced every 8 years – and for larger consumers replacement may take place as often as once a year. Even the newest, most advanced meters have an error band, because the volume to be measured and the conditions under which it is measured make a real difference.

Last but not least, apparent losses also include data handling errors (administrative losses): cases where a meter cannot be read, where the consumer does not receive an invoice for some reason, or where billing is simply incorrect because of an administrative error.

3.So does a quarter of the water really disappear?

The accurate answer is no. The vast majority of the system input volume ends up somewhere – either at the consumer (just not accurately accounted for) or serving a useful, authorised purpose such as firefighting or flushing. Water that has genuinely leaked away and been lost to the ground occurs only in the real-loss category, which is typically the larger, but by no means the only, part of NRW.

This distinction matters because repairing a leaking pipe calls for a completely different intervention than replacing an ageing water meter or correcting an administrative error – even though all of them fall into the same statistical category of NRW.

4.How big is the number in reality?

Worldwide, an average of roughly 30% of system input volume becomes Non-Revenue Water; in Europe the average is around 25%. The figure varies enormously between countries – and within countries too: in some places it is around 5%, in others it can exceed 60%.

These wide differences usually come down to the age and condition of the infrastructure, the standard of network operation, how reliably meters are read, how accurate the metering is, and how deliberately a given country invests in loss reduction.

5.Why does it matter to know this precisely?

• Our water resources are finite – every cubic metre that genuinely leaks away is a resource we cannot use.
• Water that is not accurately metered or not billed is lost revenue for water utilities, which in the long run also reduces the funds available for development and maintenance.
• Without the right diagnosis (real or apparent loss?), development budgets can end up in the wrong place – for example invested in costly, resource-intensive mains renewal where the loss could in fact be reduced by other means.
• Water utilities supply the public 24 hours a day and guarantee adequate volumes, but they cannot optimise their systems for peak demand alone, nor can they provide unlimited clean drinking water for agriculture, industry or wasteful household use.
• Once we understand how the system works, we stop passing judgement on the professionals who run it and instead support their work: we use water intelligently, and only where it is genuinely needed.

6.What can we do about it?

Targeted intervention is impossible without continuous, real-time measurement, which allows faults in our own internal network to be located and rectified in the shortest possible time.

A data logging device fitted to the water meter makes continuous oversight possible: not only can failures be detected in good time, but consumption patterns and volumes used become traceable, and savings opportunities become visible. For industrial consumers, simultaneous high-volume draw-offs stand out clearly – and these place a burden not only on the internal network but on the entire distribution system.

Fitted to existing water meters, smart metering add-ons monitor actual consumption continuously and send automatic alerts in the event of unusual consumption or continuous leakage. With smart devices, the vague sense that “the water is disappearing” and “the bill is high” gives way to precise knowledge of how much water is genuinely leaking away and how much the consumer is actually using.

This data also supports the utility's work, because it becomes visible whether the water is “merely” not accurately accounted for or has genuinely been used – with the added insight of when it was used and in what quantity. On that basis, utilities can make well-founded development decisions.

7.Frequently asked questions

8.Summary