A loss-control case turns on one question: is the missing water a billing problem or a pipe problem? The AWWA M36 balance answers it from an audit the utility already filed.
The balance
Four quantities, each from the utility’s own filing:
- System input, what went into the system.
- Authorized consumption, what was delivered on purpose, billed or not.
- Water losses, apparent plus real. Apparent losses reached a customer and were billed wrongly or not at all. Real losses leaked out.
- Non-revenue water, system input less what was billed.
Each is computed from the filing and labeled as computed; a figure the utility stated itself is a separate number with its own label. System input is taken as filed and never rebuilt from its parts, because a balance that adds up by construction cannot show a filing that does not.
The rule that decides where the money goes
Apparent losses are valued at the retail rate. The water was treated, pumped, delivered and consumed, and only the billing failed, so the utility lost the full price of it.
Real losses are valued at the variable production cost: raw water, chemicals, pumping energy. That water never reached a customer and was never revenue, so what it cost is what it cost to make.
Reversing the two overstates leakage by about a factor of three on real filings, and points the spending at pipe when the recoverable money is in meters. It is the most common error here.
A missing figure stays missing
An absent quantity is a fact about the filing, not a zero. A filing with no unbilled authorized volume gets a blank cell, because a zero would move that water into losses and inflate everything below it. Absence travels along the arithmetic and no further: a filing missing its retail rate loses only its apparent-loss valuation.
No leakage index appears on this site
The infrastructure leakage index compares a system’s real losses against what a system in good condition would lose anyway. It is the figure most readers come for, and there is none here for any system, because the filed record does not carry what the comparison needs.
An absent index says nobody filed the figures behind it. A substituted one says a named utility’s leakage is 2.4 times the unavoidable minimum. Only one is true, and in the same typeface a reader cannot tell which.
If those figures are ever published, the arithmetic is already written.