Abstract: Valve cartridge (10) includes a housing (32) having inlet member (54), outlet member (52) and screw thread (34). Cavity (36) extends axially through housing (32) within which is a piston (38) which moves axially against piston seal (44) to open and close tap (10). A flow chamber (40) is provided at the end of housing (32) and includes a first seal (42) for sealing against a valve seat (18) in the tap (10). Piston (38) can be moved axially by either a rotatable spindle (46) or, a solenoid (48) and push rod (50). Piston (38) is moved axially without any rotation. Coupling member (84) couples spindle (46) to piston (38) and rotates relative to the piston (38) and the spindle. When spindle (46) is turned a predetermined number of revolutions the coupling (84) causes piston (38) to abut piston seal (44), any further rotation of spindle (46) causes rotation of the coupling member (84) without effecting the axial position of piston (38).