Single jet water meter: When water flows through the water meter, only one (strand) water flow drives the impeller to rotate. The nominal diameter of such water meters is generally 15 (or 13) ~ 25 mm. The single jet water meter is small in size and light in weight. The counting mechanism and the testing mechanism are rotated by magnets. The counter can rotate 360° freely, which is convenient for reading. The water meter has anti-magnetic effect and can keep the reading clear for a long time. The utility model has the advantages of compact structure, high counting precision, small starting flow, beautiful appearance and reliable work.