Non-revenue water: where a city's water goes before it is billed

Non-revenue water is the water a utility treats and pumps into its network but never bills. Some of it leaks out of pipes. Some of it reaches people but is never recorded or charged. Some is used with the utility's permission, for fire-fighting or flushing mains, and simply not billed. Every litre of non-revenue water has already cost the utility electricity, chemicals and pumping, and none of it brings in money.

The water balance in plain words

Water engineers use a standard accounting table from the International Water Association (IWA), usually called the water balance. It starts with all the water put into the system and splits it, step by step, until every cubic metre sits in one box.

Put together, non-revenue water equals unbilled authorised consumption plus apparent losses plus real losses. The two kinds of loss need different fixes. Real losses are a plumbing problem: water is gone. Apparent losses are a measurement and billing problem: someone used the water, but the record is wrong or missing. The glossary has entries on the water balance and on apparent and real losses.

Why it matters to the utility and to households

For a utility, non-revenue water is lost income on water it has already paid to produce. Real losses also mean it must treat and pump more water to deliver the same amount to consumers, which raises costs and puts pressure on rivers, reservoirs and aquifers. Apparent losses mean the water arrived but the bill did not, so paying consumers carry the cost of those who are under-billed.

Households feel it in other ways. A network that leaks heavily cannot hold its pressure, so many towns supply water for a few hours a day instead of continuously. Homes at the far end of the line get a weak flow or none. When pipes empty between supply hours, dirty water from the surrounding soil can be drawn in through the same cracks that leak, which is a health risk as well as a waste. Families respond with sumps, booster pumps and overhead tanks, which adds to their own costs.

The scale: World Bank estimates from 2006

We have not found a national figure for India from an official source, so this article does not give one. A global estimate comes from a World Bank paper published in December 2006, The Challenge of Reducing Non-Revenue Water (NRW) in Developing Countries.

Its authors estimated that every year more than 32 billion cubic metres of treated water physically leak from urban water supply systems around the world, while 16 billion cubic metres are delivered to consumers for zero revenue. A cubic metre is 1,000 litres. They put the total cost of non-revenue water to utilities worldwide, conservatively, at 141 billion US dollars a year.

These are 2006 estimates. They show the size of the problem, not today's figures.

What a non-revenue water programme does

The same World Bank paper describes the methods utilities use to bring losses down. They work together rather than alone.

• District metered areas (DMAs). The network is split into zones, each fed through one or a few metered inlets. The water entering a zone can then be compared with what its consumers use, and the zones losing the most get attention first.
• Pressure management. Leaks lose more water at higher pressure, and high pressure causes more bursts. Lowering pressure where and when it is not needed, often at night, cuts both.
• Active leak detection and repair. Crews search for hidden leaks with listening equipment and sensors, instead of waiting for water to surface on the road, and repair them quickly.
• Customer meter replacement. Old or wrongly sized meters under-register, especially at low flows, and every unrecorded litre is an apparent loss.
• Finding illegal connections. Unauthorised taps take water outside the billing system. Comparing a zone's inflow with its billed use shows where to look.

Two recent examples: one programme in operation, one approved plan. Thames Water in England says in its newsroom on 24 August 2026 that it now runs over 75,000 acoustic sensors, up from 21,000 in 2025, fixes over 1,000 leaks a week, and has cut leakage by over 15 per cent since 2019/20. It adds that a satellite trial found over 800 leaks, losing about 8.7 million litres a day. These are the company's own figures.

In Delhi, ANI reported on 30 September 2026 that the Delhi Jal Board's South Delhi water project, worth ₹6,044.05 crore, covers 247 sq km, 13 underground reservoir (UGR) command areas and 2,44,381 domestic consumers. The plan includes smart meters, bulk flow meters, and chlorine and pressure sensors, with a non-revenue water target of below 15 per cent.

How household metering and remote reading help

Every method above depends on knowing how much water each connection actually uses. A working meter on each household connection turns consumption from a guess into a record. Billing then follows real use, under-registering meters show up when their readings fall out of line, and apparent losses shrink.

Household meters also make the district comparison possible. The bulk meter at a zone's inlet records what went in. The household meters inside record what was used. The gap between the two is what the zone is losing, in leaks or in unrecorded use. A housing society can do the same sum at its own scale, with its main meter against the total of its flat meters.

The comparison only works when both sides cover the same period. When household meters are read by hand on different days across a month, the totals blur. A meter that can be read remotely sends its readings at regular intervals, so the inflow and the consumption can be lined up over the same days.

Meters do not stop leaks. They show where the water is going, so that crews, pressure valves and repair budgets go where they will recover the most.