as will become clear extending radially inwardly from the shoulder 35 is a series of ribs 37 terminating in a central ring 38 or opening which continues to the central ring or opening 39 into which the inlet conduit 41 is received the ribs 37 together with the central ring 38 that part of the base 23 including the shoulder 35 and the partition member 42 define a series of chambers 43 the partition member 42 includes a series of openings 44 through which water will pass to join the outlet conduits 45 in the construction as shown there will be six openings 44 each of which feeds into one of six conduits 45 the number of conduits being even one valve may be used as a source for two or more other valves to provide equal distribution of water flow as already explained disposed above the base 23 is the modular piston housing 24 which includes the valve shut off plate 36 spaced from the floor 46 of the piston module by appropriate spacers 47 the diameter of the outer cylindrical surface 34 of the module 24 is such as to just fit easily within the inner cylindrical surface 33 the fit is sufficiently close that there is no significant leakage of fluid from the top surface of the module 24 to the bottom surface or vice versa similarly in the assembled condition the valve shut off plate 36 rests against the shoulder 35 on the outer diameter of the base 23.