This invention relates to sequencing valves and more particularly to sequencing valves which selectively direct a source of fluid to one or more of a plurality of use outlets, which operate in optimum manner for the fluid system at hand, is configured to provide anti-siphon protection when connected to municipal water supplies, and which achieve these functions while being of minimum size and weight, having a minimum of moving parts which are easy to maintain. Several different approaches have been made to provide a sequencing valve, but none have provided the features with the simplicity and compactness of the improved type disclosed herein. Classically, irrigation systems use a plurality of selectively positioned fluid distribution valves controlled remotely, either electrically or hydraulically, but such plural valve systems are more costly to install and maintain in view of the amount of apparatus and the total number of moving parts utilized. Sequencing valves which are directly controlled by solenoids have also been utilized, but have a higher pressure loss and greater complexity. Flow turbine operated valves have also been utilized but are overly complex, and subject to contamination damage, as well as lacking flexibility of timing and selection of individual zones. In accordance with the present invention, an actuation piston is positioned in the housing between the inlet port and the distributing valve member and is operatively connected to said distributing valve member to sequence this valve member into register with selected outlet ports as determined by a cam mechanism connected to said actuation piston and said valve housing, in response to pressure variations applied to said actuation piston. The actuation piston is configured so that positive actuation and sequencing is achieved before flow can pass through the valve.