AWWA M36 water audits with metered inputs, not estimates
AWWA Manual M36 sets the water audit method North American utilities use to measure non-revenue water, real losses and apparent losses. Its results are only as good as the meter data behind them. Aqueduct supplies that data by district, read alongside SCADA and AMI.
Who it applies to
Any water utility can follow M36, now in its fifth edition, and AWWA's Free Water Audit Software applies its method. Some states make the audit mandatory.
In Georgia, every public water system that regularly serves 3,300 or more people must file an annual audit using the AWWA software by 1 March, signed by a qualified water loss auditor, and run a loss control program. In California, every urban retail water supplier has filed a validated audit with the Department of Water Resources each 1 October since 2017.
What the audit requires, and the data behind it
Component names follow AWWA Free Water Audit Software v6. Your utility or auditor completes and validates the audit.
| Requirement | What it asks for | Data Aqueduct supplies |
|---|---|---|
| Water supplied | Volume from own sources and imports, corrected for master meter error. | Production and import meters with calibration checks and error trends. |
| Authorized consumption | Billed metered, billed unmetered, unbilled metered and unbilled unmetered use. | AMI and customer meter totals for the same period. |
| Apparent losses | Unauthorized consumption, customer metering inaccuracies and systematic data handling errors. | Meter drift and data gaps flagged per meter. |
| Real losses | Physical leakage, calculated as the residual of the balance. | District inflow minus metered use, with night flow per district metered area. |
| Data validity score | Each input graded 1 to 10 and weighted into a total score. | Meter coverage, interval completeness and calibration dates per input. |
| Infrastructure Leakage Index | Current annual real losses compared with unavoidable annual real losses. | Real loss volumes per year, ready for the index calculation. |
Dates and versions
People served, the Georgia threshold for a mandatory annual audit due 1 March.
Source: Georgia Rule 391-3-33Annual deadline for California urban retail suppliers to file a validated audit.
Source: California SB 555The 2025 release of AWWA's Free Water Audit Software, adding a carbon balance to the water balance.
Source: AWWARelated standards
sites in 21 countries run on Aqueduct.
and 9 clinics in one of India’s top hospital chains.
US airport running water intelligence on Aqueduct.
of commercial real estate under Aqueduct.
FMCG manufacturing campus.
operations run on Aqueduct.
Related
Common questions
It tells regulators and boards how far to trust the audit. A low score usually means estimated inputs, so a utility can report a loss figure that is precise to the gallon and still wrong.
No. The audit sizes real losses for the whole system once a year. Night flow per district metered area shows which zone the loss sits in, which is what crews need.
No. Control stays with SCADA. Aqueduct reads production, district and customer meters alongside it and turns them into a balance per district, which feeds both the audit inputs and the crews looking for leaks.
The ILI is a ratio: the leakage a utility actually has, divided by the lowest leakage technically achievable for its mains length, connections and pressure. A lower ILI means less recoverable loss. Aqueduct supplies yearly real loss volumes from measured balances. See ILI.
See Aqueduct on your own facility.
Bring a site, a utility bill or a question. We will show you where the loss is.