Water Flow Sensor Switch with Hall Effect G1 2 Inch DC 5V 1 30 Liters min

Flow range: 1-30L/min. Cumulative flow conversion: 1L water = 553 pulses. 1 xWater Flow Sensor. Long-lasting Construction: Crafted from high-quality copper with a waterproof design, the sensor effectively prevents water ingress.

eBay