Every gallon your utility produces but never bills for is revenue quietly draining out of your budget, and most managers only discover the scale of it once a rate case or board meeting forces the question. An AWWA-standard water loss audit is the only way to actually put a number on that loss instead of guessing at it. Utilities that skip a formal audit typically run non-revenue water well above the 15-25% range regulators and industry bodies consider healthy, without knowing whether the cause is leaking mains, faulty meters, or unbilled consumption. The M36 methodology, developed jointly by AWWA and the International Water Association, gives you a defensible, standardized way to quantify exactly where every drop is going, and where the recovery dollars actually are: start tracking your water balance with Oxmaint.
Conducting a Water Loss Audit With AWWA Methodology
You cannot manage water loss you have not measured. The AWWA/IWA water audit methodology turns a vague sense of "we lose some water somewhere" into a validated, line-by-line water balance that tells you exactly how many gallons are lost to leakage versus meter error, and what recovering them is worth.
Turn Audit Data Into a Live, Continuously Updated Water Balance
Oxmaint pulls production meter, billing, and consumption data into one AWWA-aligned water balance so your audit stays current between formal reporting cycles instead of going stale the day after you file it.
What the AWWA Water Balance Actually Tracks
The water balance is the backbone of the M36 method. It starts with every gallon your system produces and splits it, step by step, into water you billed for and water you lost — so nothing is unaccounted for and nothing hides in a rounding error. Building this out for your own system is exactly what a full audit walkthrough on Oxmaint's free trial will show you.
Apparent Losses vs. Real Losses: Why the Distinction Matters
The Six Steps of an AWWA M36 Audit
The Free Water Audit Software gives you the spreadsheet, but the sequence below is what actually happens behind it. Utilities that assign clear ownership to each step consistently produce more defensible, higher-grade audit data.
Stop Re-Building Your Water Balance in a Spreadsheet Every Year
Oxmaint links directly to production meters, billing exports, and work order history so steps one through five of the audit update automatically instead of consuming a week of staff time every reporting cycle.
Reading Your Results: NRW% vs. Infrastructure Leakage Index
| Indicator | What It Measures | Healthy Benchmark | Limitation |
|---|---|---|---|
| NRW as % of system input | Share of produced water never billed | Below 25% per World Bank guidance | Swings with seasonal demand, not just leakage |
| Infrastructure Leakage Index | Current real losses against the unavoidable minimum for your system | Below 2 is considered world-class | Requires accurate pipe length and pressure data |
| Gallons lost per connection per day | Real losses normalized by customer count | Utility and density dependent | Less useful for comparing rural to urban systems |
| Data validity score | Confidence grade behind each audit input | Higher band each reporting cycle | Depends entirely on metering and record quality |
A system with a high NRW percentage but newer infrastructure may still post a low ILI, meaning the loss is closer to unavoidable than it looks. That distinction is exactly why AWWA recommends reading the two indicators together rather than reacting to NRW percentage alone.
What Utilities Recover Once the Audit Points to Real Numbers
Frequently Asked Questions
How often should a water loss audit be conducted?+
What is the difference between NRW and the Infrastructure Leakage Index?+
Do I need the AWWA Free Water Audit Software to follow this methodology?+
What data validity grade should a utility be targeting?+
Can a small utility complete this audit without dedicated staff?+
Your Next Water Loss Audit Doesn't Have to Start From a Blank Spreadsheet
Oxmaint keeps your system input volume, billing data, and leak history connected year-round, so every AWWA audit cycle starts from a validated water balance instead of a week of manual data assembly.
