EU leakage assessment, by ILI.

What the directive actually changed

Directive (EU) 2020/2184 recast the EU’s drinking water rules in 2020. Most of the attention went to the parameters at the tap. The quieter change was Article 4(3): for the first time, how much water leaks out of a network on the way there became something a member state has to measure, evidence and report.

The method is named. Leakage is assessed using the Infrastructure Leakage Index, or another method of comparable rigour. That matters more than it sounds, because ILI is a ratio rather than a percentage, and a ratio survives comparison between countries in a way that “we lose 18% of system input” does not.

One distinction worth keeping straight: the obligation belongs to the member state, not to you. No utility is required by Brussels to file anything. But a national authority cannot report a number it does not have, so the requirement lands on utilities anyway, through whatever national instrument was used to transpose it.

Who is in scope

The assessment has to cover at least water suppliers distributing 10,000 m³ per day or more, or serving 50,000 people or more. That is a floor, not a ceiling – some member states collect from a wider set. A mid-sized municipality is often just under it and asked anyway, because the national authority would rather have the coverage.

The timetable

1. 12 January 2026 – done. Member states had to communicate their leakage assessment to the Commission. This date has passed; most of the work now visible in the sector is the second round of it, and utilities that supplied a weak first number are being asked for a better one.
2. 12 January 2028. The Commission adopts a delegated act setting a threshold, based on ILI or another appropriate method.
3. After the threshold lands. Member states above it have to present an action plan. That pushes the work back down to the utilities that make up the national figure.

The gap between now and 2028 is the useful part. A utility that spends it turning an annual estimate into a measured, zone-level balance arrives at the threshold with a defensible number and a trend. One that waits arrives with a spreadsheet.

What you need in place to produce the number

An ILI is only as honest as the water balance underneath it, and a water balance needs four unglamorous things.

1. Every input measured. System input meters on each source into the network, reading reliably. A balance missing one input is not a balance.
2. Zones that are real. The network divided into districts with known, actually-closed boundaries. One partly open valve moves a neighbour’s consumption into your loss figure.
3. Readings on one clock. A zone meter read at midnight against customer meters collected over three weeks compares two different stretches of time, and the remainder is arithmetic noise. Synchronise first, subtract second.
4. Real losses separated from apparent ones. ILI is about real losses – water through a hole. Meter under-registration, unauthorised use and data-handling errors are apparent losses, and counting them as leakage sends crews to look for a pipe problem that is sitting in the accounting.

Water loss management on Divako is built around exactly these four, and non-revenue water for municipalities walks through what the balance is made of.

What to watch out for

• A first ILI is usually wrong, and that is fine. The first number a utility computes is generally a statement about its data quality rather than its pipes. Publish it internally, find what it is really measuring, and improve the inputs before the number goes anywhere official.
• Apparent losses flatter and punish at random. An ageing meter fleet that under-registers at low flow moves water from “billed” into “lost” and inflates your real-loss figure. Check meter age and drift before you conclude the network is leaking.
• UARL is sensitive to pressure. The unavoidable-losses denominator depends on average operating pressure, so a pressure figure that was assumed rather than measured moves the ILI without anything changing in the ground. Measure it.
• Do not quote a 2028 threshold. It does not exist yet. Plan for the mechanism – assessment, threshold, action plan – and leave the number blank until the delegated act is published.
• Transposition varies. The directive sets the floor; national law sets what your regulator actually asks for, in what format, and how often. Check the national instrument, not just the directive.