The free water balance calculator for non-revenue water, leakage and carbon
Build an IWA-standard water balance in about ten minutes. Get real and apparent losses with honest uncertainty bands, the Infrastructure Leakage Index, the annual cost of non-revenue water and the carbon footprint of leakage. Missing a number? The built-in assistant suggests a defensible value for your country and system — and writes the findings for your board.
No sign-up needed to run one. Create a free account to save it, export to Excel, or import a WB-EasyCalc file.
The balance fills in as you type. Hatching is the 95% uncertainty band.
Every IWA component, with uncertainty
System input, billed and unbilled consumption, unauthorised use, meter under-registration, data-handling errors and real losses as the residual. Each carries a ±95% band, propagated properly, so you know how much to trust the leakage figure.
Indicators that mean something
CARL, UARL and ILI; litres per connection per day when the system is pressurised; NRW as a share of input and of operating cost. Placed on the World Bank Institute matrices for standard and low-and-middle-income systems.
Money, carbon, and what-if
Value each component at tariff or marginal cost. See tonnes of CO₂ embodied in leakage by treatment process. Then move the levers — pressure, supply hours, target ILI — and watch NRW, revenue and carbon respond.
AI-assisted, so gaps in your data don't stop you
Most water balances stall on the numbers nobody has: meter under-registration, illegal connections, service pipe length, marginal cost. Next to each of those inputs is a “Help me estimate” button. Tell the assistant what you know, and it proposes a value with a ± band and the reason — drawing on what is typical for your country, climate and system type, and on what is publicly known about your utility. Accept it with one click, or use it as a starting point.
When the balance is done, it can draft the findings: a structured summary of the balance, the ILI and NRW bands, the cost and carbon, and the highest-value actions — ready to review and drop into the PDF report.
Suggestions are starting points, never substitutes for your data. Every accepted value stays visible in the inputs appendix of the report.
Example — Apparent losses step
What overall customer meter under-registration % should I assume?
What I know: regional Queensland council, meters at the boundary, about 30% of meters over 12 years old.
How it works
- Step 1
Water in
Enter each source with its volume and metering accuracy. Pick a treatment category and the carbon factor is applied.
- Step 2
Consumption and losses
Billed and unbilled use from the billing system; estimates for illegal use and meter under-reading — with help if you need it.
- Step 3
Network and pressure
Mains length, connections, service-pipe length and zone pressures set the unavoidable leakage for your system.
- Step 4
Results
The full balance in m³ and tCO₂, the indicators, the bands, the cost, a what-if table and a findings narrative you can put in front of a board.
Understand the numbers
Non-revenue water (NRW): what it is and how to calculate it
NRW is the water a utility puts into supply but never bills. Learn the IWA definition, the formula, what counts as apparent versus real losses, and why percentages mislead.
Infrastructure Leakage Index (ILI) explained
The ILI compares your current real losses with the unavoidable minimum for your network. Learn the formula, the World Bank bands from A1 to D, and what your ILI tells you to do next.
The UARL formula: unavoidable annual real losses
UARL = (18 × Lm + 0.8 × Nc + 25 × Lp) × P. What each term means, where the coefficients come from, and how supply time and pressure change the answer.
Apparent losses: meter under-registration, illegal use and data errors
Apparent losses are water consumed but never recorded. How to estimate customer meter under-registration, unauthorised consumption and billing data errors for a water balance.
Water audit vs water balance: IWA and AWWA M36 compared
The IWA water balance and the AWWA M36 water audit are the same idea with different vocabulary. Here's how the terms map and how to move between them.
The carbon footprint of leakage and non-revenue water
Every cubic metre lost to leakage carries the energy and chemicals it took to treat and pump it. How to estimate the tCO₂ embodied in real losses using treatment-process carbon factors.
Questions people ask
- What is a water balance?
- A water balance accounts for every cubic metre put into a distribution system over a period: what customers used (billed and unbilled, metered and unmetered), what was lost to leakage (real losses) and what was consumed but never recorded (apparent losses). The IWA standard water balance is the internationally accepted format.
- How is non-revenue water (NRW) calculated?
- NRW = system input volume − billed authorised consumption. It includes unbilled authorised consumption, apparent losses and real losses. This calculator reports NRW as a volume, as a percentage of input, per service connection per day, and as an annual cost.
- What is the Infrastructure Leakage Index (ILI)?
- ILI = current annual real losses ÷ unavoidable annual real losses (UARL). The UARL is the technically achievable minimum leakage for your network's length of mains, number of connections, service pipe length and average pressure. An ILI of 1 is world class; above 8 means leakage reduction is urgent.
- Is this the same as WB-EasyCalc?
- It implements the same IWA methodology — the standard water balance with 95% confidence limits, the Lambert UARL formula, the World Bank Institute performance bands and a carbon balance by treatment process — as a web app with guidance built in. You can import an existing WB-EasyCalc or WCB-EasyCalc workbook.
- How does the AI assistant help?
- Beside each hard-to-source input is a 'Help me estimate' button. The assistant proposes a value with an uncertainty band and a one-line justification, using what is typical for your country, climate and system type and what it knows about your utility. It can also draft a structured findings summary from your results. Suggestions are starting points and are always visible in the report's inputs appendix.
- Is it really free?
- Yes. The calculator, saving, Excel export and the AI assistant are free. Creating an account lets you save balances and come back to them.
- Does it work in US gallons?
- Yes. Switch to US customary units and enter million gallons, miles and psi. Calculations follow the same IWA / AWWA M36-compatible top-down approach.