This 4-way electromagnetic valve is typically used on a Di Vapor steam shower to control water flow to the upper body, middle body and lower body jets along with the overhead rainfall shower.If one of these features is failing then it is likely that one solenoid block within this 4-way set has failed. Typically, the whole set is changed at the same time although it is possible to change a single block. Failure can sometimes be caused by water leaking onto the electrical solenoid.An electromagnetic valve or solenoid acts as an electrical switch. This means that water features can be switched on or off using the control panel. The input supply should be 12V DC and each solenoid has 2 connectors.The width of the water connector is approximately 26mm or 1.02 inches. We have a reducer connector which screws onto the end of this which reduces the connection to 20mm or 0.8 inches. You can purchase the reducer here.