A Volumetric Water Meter is a kind of residential or domestic water meter, and it is fitted into a closed conduit, which consists of chambers of known volume and a mechanism driven by the flow, whereby these chambers are successively fitted with water and then empited. The water to be measured enters the inlet of the body and its pressure sets the piston into rotation. Every rotational cycle of the piston discharge a fixed volume of water to the meter of body. The number of rotation of the piston is totalized through a reduction gear to totalize in the register, when the total volume of water is registered.