What NMX-AA-179-SCFI-2018 is

NMX-AA-179-SCFI-2018, “Measurement of volumes of national water used, extracted or exploited”, is the technical reference against which the authority judges whether a water use is measuring properly. ¹

What it covers

Not just the device. The standard reaches the meter, the metering system it belongs to, how it was chosen, how it was installed, how it operates and how the data it produces is transmitted. A correct meter badly installed does not comply, and a system that measures well but does not transmit does not either. ²

What conformity assessment means

The standard does not enforce itself. That check is called conformity assessment, and it consists — literally — of visually attesting and verifying that the meter, the metering system, its selection, installation, operation and data transmission satisfy what the standard specifies. ²

Who may assess it

Only a Verification Unit accredited by the Mexican accreditation body and approved by CONAGUA, and only through individuals holding a current certificate from the Ministry of Public Education in the relevant competence standard. Neither accreditation nor approval alone is enough: both are required, plus certified personnel. ³

What it requires of equipment

For the meters covered by clauses 6.1 and 6.2, verification uses calibrated measuring instruments and standards, backed by a laboratory report or a current calibration certificate from an accredited laboratory. The metrological characteristics the equipment must meet are set out in Appendix A of the standard itself. ²

Where the data ends up

Clause 10.8 governs the transmission of measurement data to CONAGUA. For that transmission each approved Verification Unit carries a number assigned by the authority; NEOMETRIC MEXICANA’s is 017. ²