Question
Have watermiser control valve to drip,,quit dripping, replaced to head and diagham and hear water going thru valve but at a reduced pressure,,not enough to put water thru drips...the water thru the antisiphon comes out of of opening with the cap off at about 1/3 flow,,,there is a pinhole size hole in the antisiphon cartridge, cant believe that is the problem,,,any ideas

Answer
Hi Gary

The pinhole is the likely culprit.  If the check valve in the cartridge cannot seal completely, it will run on and on because of a lack of pressure required to close it.  

This could also be caused by either a call for more water than the source can supply, or a restriction of flow limiting the dynamic pressures below the ASV's working minimum pressure rating.  Also take note of the ASV installation height - it must be a minimum of 12" above the highest emitter's elevation.

Ensure there are no issues with the point of connection.  Check for pipe leaks or breaks, as well as fittings.  Ensure the valve which supplies water to the irrigation system is fully open as well.

Hope this helps

Tony