Infrastructure Leakage Index: A Guide for Australian Utilities

Water loss percentages can be useful, but they rarely tell the full story.

For Australian utilities, the Infrastructure Leakage Index (ILI) provides a more accurate benchmark for real losses and helps determine whether leakage is within a reasonable range.

In this article, you will learn:

By the end, you will have a clearer view of how to interpret ILI and what to do with it.

What Is the Infrastructure Leakage Index?

The Infrastructure Leakage Index (ILI) is a benchmark used to measure how efficiently a water network is controlling real losses. It compares the amount of water currently being lost through leaks with the level of leakage that would still exist in a well-managed network of that size and type.

In simple terms, ILI helps answer this question: how much leakage is occurring beyond what is realistically unavoidable?

That makes it more useful than looking at water loss as a percentage alone. A percentage can be misleading because it does not account for factors like network length, number of connections, or operating pressure. Two utilities may report similar water loss percentages while performing very differently in practice.

ILI focuses specifically on physical leakage from pipes, fittings, service connections, and storage assets. It does not measure non-physical losses such as metering errors, billing issues, or unauthorised use.

For Australian utilities, ILI is a practical benchmarking tool. It helps teams understand whether leakage performance is broadly under control or whether closer investigation, targeted intervention, or better data is needed.

Why Percentage Water Loss Is Not Enough

Water loss is often reported as a percentage, but that figure on its own can hide more than it reveals. A network losing 8% of supplied water may appear to be performing well, while another losing 12% may appear inefficient. In practice, those numbers do not account for differences in network size, connection density, operating pressure, or system layout.

That is the problem with percentage-based reporting. It treats very different networks as if they operate under the same conditions.

ILI gives utilities a more meaningful benchmark because it focuses on real losses in context. Instead of asking what share of water is being lost, it asks whether the level of leakage is high or low relative to what would be expected in that specific network.

For Australian utilities, that makes ILI far more useful for performance assessment. It supports better comparison across systems, helps avoid misleading conclusions, and gives decision-makers a clearer view of whether leakage is within a reasonable range or needs action.

How ILI Is Calculated

ILI is calculated by dividing Current Annual Real Losses (CARL) by Unavoidable Annual Real Losses (UARL).

ILI = CARL / UARL

Put simply, it compares the leakage a utility is experiencing now with the lowest level of real loss that would still be expected in a well-managed system. If the result is close to 1, the network is operating near its unavoidable level of leakage. A higher result suggests there is more recoverable loss in the system.

The formula itself is straightforward. The harder part is producing reliable inputs. To calculate ILI properly, utilities need accurate data on real losses, network length, number of service connections, average pressure, and other core system characteristics. That is why strong water balance calculations are such an important starting point.

That is why data quality matters so much. If the underlying leakage, asset, or pressure data is incomplete or inaccurate, the final ILI figure can point teams in the wrong direction. Used with good data, ILI becomes a practical benchmark rather than just another reported number.

How to Interpret ILI in an Australian
Utility Context

ILI is useful, but it only becomes meaningful when read in context. There is no single score that tells every Australian utility whether leakage performance is good or bad. A regional network, a dense metro system, and a mixed network with older assets may all produce very different results for valid reasons.

That is why ILI should be used as a benchmarking tool, not a standalone verdict. It is most useful when utilities compare performance over time, across pressure zones or DMAs, and against similar network types rather than treating one number as the full story.

For Australian utilities, the real value of ILI is in what it helps reveal. A rising ILI may point to growing leakage pressure, deteriorating assets, slower response times, or hidden losses that are not being picked up early. A stable or improving ILI can show that leakage programs, repairs, or pressure management strategies are working. The number matters, but the trend and the network conditions behind it matter more.

What ILI Can and Cannot Tell You

ILI is a useful benchmark, but it does not explain the cause of leakage on its own. It can show that real losses are higher than they should be, but it cannot tell you whether the issue is driven by pressure, hidden leaks, recurring bursts, ageing assets, repair quality, or incomplete data.

That is why ILI works best as part of a broader leakage performance framework. It gives utilities a strong starting point for understanding whether the network is underperforming, then other data points help explain why.

Used well, ILI can support benchmarking, trend analysis, and prioritisation. Used on its own, it can oversimplify the problem. A utility may know its ILI is high, but still need pressure data, minimum night flow trends, burst history, or zone-level monitoring to decide what action to take next.

In other words, ILI is a strong indicator, not a full diagnosis.

Common Reasons ILI Is Higher Than Expected

A high ILI usually points to leakage that sits above what should be expected in a well-managed network. Common reasons include:

Excess pressure – Higher pressure can increase background leakage and place more stress on pipes, joints, and fittings. A more structured approach to water network pressure management can often make a measurable difference.
Hidden leaks – Not all losses come from visible bursts. Small or underground leaks can persist for extended periods before detection.
Slow response and repair times – The longer a leak remains active, the more water is lost. Delays in repair can quickly lift total real losses.
Recurring asset failures – Repeated issues on the same mains or service connections often point to a broader infrastructure problem rather than an isolated event.
Ageing or deteriorating infrastructure – Older assets may be more prone to leakage, especially where renewal programs have not kept pace with condition decline.
Limited network visibility – Without strong monitoring at zone or DMA level, it becomes harder to identify where losses are occurring and which areas need attention first.
Poor data quality – Inaccurate flow, pressure, or asset data can distort the benchmark and make it harder to diagnose the true source of poor performance.

A high ILI does not tell you which of these issues is driving the result, but it does show that closer investigation is needed.

What to Do When Leakage Performance Is Off Track

If ILI is trending higher than expected, the next step is not to react blindly. It is to work through the likely causes and confirm where action will have the biggest impact.

Start with the basics:

Check the data first – Confirm that flow, pressure, consumption, and asset data are accurate enough to support the benchmark.
Look below the network-wide number – Review performance by DMA, pressure zone, or service area to find where losses are concentrated. This is where well-designed district metered areas can add real value.
Assess pressure conditions – High or unstable pressure can quietly drive ongoing leakage and repeat failures.
Review leak detection and repair practices – Hidden leaks, delayed response times, and repair quality can all lift real losses. In some cases, real-time leak detection can help utilities respond earlier and prioritise more effectively.
Compare with asset condition data – Repeated issues in the same areas may point to renewal needs rather than isolated faults.
Track trends over time – A one-off result matters less than a pattern. Trend data helps show whether performance is improving or slipping.

ILI is most useful when it leads to focused action. The goal is not just to report leakage performance, but to identify what is driving it and where intervention will deliver the best return.

Why Data Quality Matters for Benchmarking

ILI is only as reliable as the data behind it. If a utility is working with incomplete flow records, inaccurate pressure data, outdated asset information, or gaps in consumption reporting, the benchmark can become less useful and harder to trust.

That matters because ILI is often used to support real decisions. Utilities may rely on it to assess performance, prioritise leakage programs, justify investment, or report to leadership. If the inputs are weak, the result may point teams in the wrong direction or hide the areas that need attention most.

Good benchmarking depends on having consistent, connected, and up-to-date network data. That includes not just system-wide figures, but the supporting detail needed to understand what is happening across zones, assets, and operating conditions. Better pressure flow and logging can play an important role here.

For Australian utilities, better data does more than improve reporting accuracy. It improves confidence. Teams can benchmark leakage performance more clearly, identify issues earlier, and make decisions based on evidence rather than assumptions.

How Better Benchmarking Supports
Smarter Utility Decisions

Better leakage benchmarking does more than improve reporting. It helps utilities make clearer, more targeted decisions across operations, planning, and investment.

When ILI is backed by reliable network data, teams can see whether leakage is stable, improving, or drifting away from expected performance. That makes it easier to prioritise pressure management, leak detection, repairs, and renewals based on actual need rather than assumptions.

It also gives decision-makers a stronger basis for investment. Instead of relying on broad system averages, utilities can link leakage performance to specific zones, assets, or operating conditions. That leads to more focused programs and a better return on both operational and capital spend.

For Australian utilities, this is where benchmarking becomes genuinely valuable. The goal is not just to know the number. It is to use that insight to reduce avoidable loss, support long-term planning, and make smarter decisions across the network.

Turn Leakage Benchmarking Into Better Network Decisions

ILI is useful because it shows whether leakage performance is where it should be. What it does not do is tell utilities where losses are occurring, which assets or zones are contributing most, or what action should come first.

That is why benchmarking only becomes valuable when it is connected to broader network insight. When utilities combine leakage metrics with stronger visibility across pressure, flow, asset condition, and zone-level performance, they can move beyond broad reporting and start identifying the factors driving avoidable loss.

For Australian utilities, that means more than simply knowing performance is off track. It means having a clearer basis for prioritising investigations, targeting investment, and supporting better operational and planning decisions across the network.

How Aqua Analytics Helps Utilities Act on Leakage Data

Most utilities already have data. The challenge is turning that data into clear, practical direction.

A high ILI can show that leakage performance is off track, but it does not show where to focus first, what is driving the result, or how to respond in a way that delivers measurable improvement.

Aqua Analytics helps utilities close that gap. We support the full process, from water balance and NRW analysis through to DMA monitoring, pressure and flow insights, leak detection, and ongoing network visibility.

A key part of this is AquaNRW, our water loss software designed to help utilities, councils, and asset owners track ILI, minimum night flow, and leakage volume, while using DMA pressure data and a unified view of network inputs to highlight areas that need attention.

For utilities under pressure to reduce losses, justify spend, and make the most of limited resources, that matters.

Better visibility means faster decisions, stronger field prioritisation, and more confidence when planning operational or capital responses.

We help turn leakage metrics into action, so teams can focus effort where it will have the greatest impact.

If your utility needs a clearer view of leakage performance and the data behind it, contact us today to discuss how we can support smarter benchmarking and more targeted network action.

Infrastructure Leakage Index Explained: How Australian Utilities Benchmark Performance