What is AWWA M36 water audit?
The AWWA M36 water audit is the American Water Works Association method that divides a water system's input volume into authorized consumption, apparent losses and real losses to quantify non-revenue water.
Who uses the M36 audit
Drinking water utilities run it annually, and states including Georgia and California require audits in the AWWA format. A municipal loss control program starts from the audit, then works each loss type: meter testing and billing fixes for apparent losses, and district metering, pressure management and faster repair for real losses. Campuses and airports with private networks can run the same balance internally.
The balance and the software
- System input volume, corrected for production meter error, equals authorized consumption plus water losses.
- Apparent losses are customer meter under-registration, data handling errors and unauthorized use. Real losses are leaks, bursts and storage overflows.
- Real loss is the remainder once every other component is entered, so weak inputs inflate or hide it, per AWWA.
- The manual is in its fifth edition. Free Water Audit Software version 6.0 was released in 2020 and version 6.1 in 2025, adding a carbon balance for emissions from leakage.
The same balance on a single site
Aqueduct's water twin writes the balance as an equation: main supply equals all floors plus fire system plus RO feed plus unaccounted loss, refreshed every 60 seconds. The unaccounted loss term plays the role of real losses, and a rise points to a specific segment rather than a year-end estimate.