This flow switch is commonly found in Sundance, Jacuzzi, Hot Spring and other spa manufacturers. It comes with a 1-metre cable, with a 3-pin female plug.
The transparent plastic tee allows you to see the position of the reed switch. It has barbed pipe connections for 3/4" flexible pipe. The same flow switch is also available in a tee, also transparent. The switch is not currently available as a standalone part, without any pipe mounting.
Length: 125 mm
Diameter of the barbed connections: 22 mm
Outside diameter of the thread on the detector: 27 mm
Flow switch dimensions (size "Medium", in red on the diagram)
Thread diameter: 27 mm
Body length: 35 mm
Total height: 63 mm
Harwil (flow switch only): Q-12DS-C2
Harwil (flow switch + tee): Q12DSCSLA
Note that there are several versions of this Harwil flow switch, all bearing the reference Q-12DS-C, with different thread lengths and sizes (see diagram opposite). This is the "Medium" size, in red on the diagram, which is not compatible with this Harwil flow switch for Astrel heaters (which is in "Large" size), although it has the same reference.