Hello,

I am in the process of installing an anti-siphon valve for my home irrigation system. Everyone says it needs to be 6" above the highest sprinkler head. My question is: Does this mean the height of the sprinkler head in the up position or the height of the sprinkler head when the lawn isn't being watered?

Thanks,

Seth

Welcome back to the web site,

The bottom of the anti-siphon valve MUST be 6 inches higher than any of the drip emitters or sprinkler heads it operates. That means that it must be installed above ground. Do not install any anti-siphon valve below ground level or where it might be submerged under water. I suggest installing the anti-siphon valves at the highest point in the yard. Run a mainline from your water source to the high point in the yard. Then install the anti-siphon valves above ground at that high spot. From the anti-siphon valve run pipe to the sprinklers or emitters.

Note that if the sprinklers or emitters are higher than the anti-siphon valve, the backflow preventer part of the valve will not work! Water will run out of the vents on the anti-siphon valve if there are sprinklers or emitters higher than it. If more than a tablespoon of water spills out of the anti-siphon valve vent, it almost always means the valve is not properly installed.


Open the link below and you can see how to install the valve, good luck.

John

Anti-Siphon Valve Installation Details - Landscape Irrigation System Installation Tutorial

Great, thank you.

Hi all...

Only thing I might add to John's post is that if you live in a cold climate I would install unions on the anti.-siphon valve so you can remove it easily at the end of each season. If you live in warm climate this may not be necessary, except that down the road when the valve does need to be replaced it will be very easier to replace if you install unions now.

You wouldn't believe how many times I had to repair/replace these because they had small amount of water trapped in between parts... and water froze over the winter and blew them apart. They are not cheap to replace.

Just F.Y.I.

MARK

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Excellent advice Mark, Thanks.

Regards,
John

The good news is I'm near Sacramento, CA, so freezing temperatures shouldn't be much of a concern. Thanks for the advice though,

Seth

2 questions for Mark and John regarding this thread:

1. If you have 2 valves in different places at different elevations, is it true that each valve only needs to be higher than the highest sprinkler that it services? I would like to split the supply line and service 2 different areas. Its easier to run electric wire than PVC.



2. any pipe above ground has to be copper, correct? If so, that means the pipe in and out of each valve has to be copper, as well as the suggested union for each valve (at $16+ each). I suppose I could use PVC on the sprinkler-side of the valve and thus use a $5 union for each valve and replace it every (?) years when it fails... Or is it acceptable to run PVC to and from the valve if they are protected from the sun? I've seen it done...


Thanks!

PWD...

I am afraid that I cannot answer the question as I have never really piped up underground sprinklers. I have installed plenty of vacuum breakers, but have never seen systems split into 2 zones. All that you suggested seemed reasonable, though.

Hopefully others will pop in on this. If they don't post the question as a new question at plumbing and we'll see who the sprinkler guys are... O.K.

MARK