Fafeicy YF-DN40 Water Flow Hall Sensor, 5-150L/min Water Flow Meter Flowmeter Counter, Water Flow Switch, Magnetic Water Sensor Switch with G1.5in Male Thread Interface : Amazon.co.uk: Business, Industry & Science
Plastic Flow Controls - PVC Select
Flow switches, flow monitors | SIKA
FS15A Sensata / Cynergy3, Flow Switch, FS Series, 0.3 to 2 l/min | Farnell UK
Series P5 PVC Shuttle Flow Switch | Dwyer Instruments