Unaccounted-for water is the metric Massachusetts uses. MassDEP requires municipal public water suppliers averaging 100,000 gallons a day or more to calculate UAW and residential gallons per capita per day in the Annual Statistical Report filed through eDEP, and both are Water Management Act performance standards tied to withdrawal permitting.
Not interchangeable with non-revenue water
UAW is a subtraction: system input minus everything the supplier can account for, including authorized unbilled uses it can document. Non-revenue water under the AWWA framework is a decomposition into named components with an uncertainty attached to each.
The practical difference is what happens to a volume you can explain but cannot prove. Under UAW, documented estimated municipal use comes out of the numerator — and MassDEP’s own instructions are explicit that use claimed without attached documentation is counted as unaccounted-for. So the metric rewards recordkeeping as well as tight pipe, and two suppliers with identical physical losses can file materially different UAW.
Comparing a Massachusetts UAW figure to a Texas non-revenue water figure without saying which is which produces a ranking that means nothing. Our state pages keep them separate and label them.
Verify the threshold before you cite one
The numeric performance standards attach to permits and are revised. If you are about to tell a board it is over its standard, get the current number from MassDEP with a date on it. Being right about the direction and wrong about the threshold is worse than saying nothing.