Hi Dan It is a lack of adequate flow, not adequate pressure (although they can be related) that prevents the valve from indexing properly. We make an electronic monitor for these valves which confirms that they are indexing evenly and are not getting stuck due to debris in the valve, broken spring, etc. In general we find these valves are very reliable and work well as long as they are being operated within their intended design parameters. KRain say a minimum of 10 gpm is necessary for the valv...
