Leaking Shutoff Valve

Hi,

I use two (of the same) anti-siphon shutoff valves for my front lawn. One works fine, but when the second one shuts-off, a small amount of water extrudes from the outlet-side. I attached a picture to try to clearly show where it's leaking from. It's leaking from just under the smooth disk with the company logo/part # (not from threads of the anti-siphon cap).

Any thoughts on why this leak would happen for this valve, and not the others directly next to it? Can this be fixed without installing a new valve?

Thanks,
Greg

These can be repaired without removing the valve. I admit that I have never done the repair work on valves, I hire a pro to do it. I don't think it's really rocket science, but it is something that does not occur very often, and I just don't feel the need to try to remember just how to do the work. Given the fact that you seem to know even less about these valves that I, I'd advise a pro.

The valve is supposed to leak from there if there is a back siphonage event.

Chances are this particular valve is leaking(after shut off) because a sprinkler head(or heads) on that zone are installed "higher" than the valve.

Modern spring-loaded rotor heads will be able to push some water backwards towards the valves when the zone shuts off, so this is not a definite indication of a malfunction.

Thanks tomm and all,

Yes I think height is the issue. The yard runs downhill and the valve that isn't leaking controls the lower portion of the yard. The one that leaks has a sprinkler head that is close to, maybe breaking, the 6" below valve rule.

The fix for this would be to lop off the valve, glue in some a couple extra inches a straight PVC pipe for added height and reattach the valve, correct?

Actually the more I look, the sprinkler that is taller than the valve is a fixed (non-pop up) head mounted on a piece of 1/4" pipe, and it's not even that useful. Will just replacing the sprinkler head with a cap solve height/siphon problem?

Out of curiosity what would happed if it was left as is? Is the water that is leaking out of the AVB top the water was back-siphoned out from the sprinklers (and not making it's way further back upstream to the contaminate the water supply)? Would that part of the valve (i.e. the float) eventually fail and allow backflow?

So I took off the sprinkler-head off the piece of pipe that was too tall, relative to the shut-off valve, and replaced it with a pipe cap. That eliminated the water coming out of the AVB cap upon shut off. Verified with several uses.

Is that enough? Or do I need to fully remove the offending pipe and plug it at the base to completely eliminate the threat of back-siphoning?

You can have a proper installation of antisyphon valves, and still get some water gurgling out at shutdown.