Large-scale reception testing reveals initial metrological non-compliance in brand-new domestic water meters

Reliable domestic water metering is essential for billing, demand assessment and water-balance analysis, yet the initial metrological performance of brand-new meters remains poorly documented. This study analysed a historical reception-control database of 1,922 brand-new domestic water meters tested under controlled laboratory conditions using an accredited gravimetric test bench. The samples included single-jet, volumetric and ultrasonic meters. A meter was classified as non-compliant when at least one measured error exceeded the applicable maximum permissible error at any tested flow rate. Overall, 207 m were non-compliant, corresponding to a non-compliance rate of 10.8%. Non-compliance differed strongly by technology, reaching 33.8% for single-jet meters, 8.7% for volumetric meters and 2.7% for ultrasonic meters. Error patterns also varied by anonymised manufacturer code and metrological ratio (R). Within volumetric meters, manufacturer-code non-compliance ranged from 3.1 to 30.6%, while non-compliant single-jet meters showed marked negative bias, highlighting supplier-specific and pre-installation under-registration risks. Extended testing was associated with improved diagnostic resolution in some groups, although its marginal detection benefit depended on sample composition and error location along the flow-rate range. These findings show that reception testing provides diagnostic information that cannot be inferred from certification or nominal specifications alone.