Rotary piston type water meters are very accurate in small sizes and widely used in 1/2" (15mm) to 2" (50mm) sizes for residential uses.

Rotary piston type water meters use water to push a piston. The piston rotation speed is in relation to the velocity of water flow.

Rotary piston type water meters generally have an internal strainer element that can protect the pistons from getting clogged.