Does anyone know what this electric part does? In the photo it's the black plastic block device attached to the pipe on the right hand side (which is the mains inlet to the heater; the left is the hot outlet). It looks to me like a solenoid valve, but neither the instruction manual for the heater nor for the washing machine mention it.
The heater is a ZIP Aquapoint III 30L unvented electric water heater that used to supply a Maytag stacked washer/dryer unit. On that machine, the part was electrically connected to a terminal on the washing machine itself. Somebody else since replaced the washing machine and left that part attached to the inlet pipe, and there's no obvious terminal on the new washing machine to connect the part to. The bottom part of the device with the wire sticking out is a removable power plug with three terminals.