If a water meter with a dry dial (e.g., model GSD8 / GMDM / WDE-K50) does not register consumption despite the presence of flow (no rotation of the rollers/hands), one possible cause could be water hammer caused by too rapid opening of the valve/pump.
In dry dial meters, the transmission between the turbine and the clock mechanism occurs through magnetic coupling.
The magnet inside the turbine, when rotating, drives the magnet coupled to the clock mechanism, allowing consumption to be recorded.
A water hammer could temporarily decouple the magnetic connection between the clock mechanism and the turbine, causing a "slip" resulting in failure to record the volume passed.
If this phenomenon occurs, our advice is to open the valve more slowly, allowing a more controlled change in water velocity, limiting the risk of such decoupling.