shrub sprinkler much higher than anti-siphon valve - problem?

trojan09July 23, 2010

Hello everyone,

We recently bought a new home and I have been inspecting the existing sprinkler system. The system currently has manual valves and I wanted to upgrade them to automatic. As I began reading up more about valves and sprinkler systems, I noticed that the system currently has anti-siphon valves installed. Now in all the instructions for anti-siphon valves that I've seen, it says the valves MUST be 6" above the highest sprinkler head. However, in both the front yard and the back yard (separate valves), there is at least one shrub sprinkler. The shrub sprinklers are 3-4 feet tall. The anti-siphon valve is no more than 6" above ground level, if that. Is this a botched job? Whenever I manually stop the sprinklers, I notice a rapid splash out of water from the outlet side of the valve. Am I right in assuming this is a backflow event being prevented by the valve? Should I remedy this situation? What are my options? I suppose I could raise the valve to above the shrub sprinkler, but it seems like it would be weird to have this 5 foot tall valve up in the air against the house wall. What do most people do in this situation? Should I just cut down the shrub sprinklers? Or perhaps there are other valves that do not have this height restriction? Does that anti-siphon backflow preventer still work or am I currently at risk of contaminating my water supply?

Thank you so much for any and all suggestions.

An irrigation newbie

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You have the proper idea here and you have read the literature. Yes there is a possibility that the high heads could cause siphoning back to the house or street mains. Yes the burst of water is from the anti-siphon working properly. Yes the installer didn't pay much attention to the regulations(not news). Yes there are other types of anti-siphoning valves but most are not as reliable as the anti-siphon valves and hard to verify they are not working. Sometimes local city/county ordinances spell out the requirements for irrigation systems and alternate valve choices and everything else. Yes your yard would be an unusual case(steep grade changes) by having 5 foot high valves but not unheard of. Your situation would also require higher pressure for the system which may or may not be a good thing. A valve that can be utilized in your situation may be small check valves on the lines to the high irrigation heads( leaves water in the lines) and cuts down on head noise at start up. With all that said, I believe (others may disagree)the height of the tee at the bottom of the irrigation head should be below the anti-siphon valve. My A-S valve is about 24" above the ground as it come off my house hose faucet(aesthetically handicapped) and then goes into a auto-valve manifold in a irrigation control box with the lid about 1 inch above the ground. JMHO Aloha

    Bookmark   July 25, 2010 at 11:09AM
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Hi! I am installing a system for my recently inproved yard. I have a pond with a watterfall from a terraced section behind it. This area is about 2'-8" above grade, and I was just reading up on whether or not I should ignore the recommendation and assume an extra 3' of pressure (about 1 psi) won't hurt.

That said, I do believe the highest sprinkler is technically the important one. This is because air can enter through the sprinkler, allowing water to flow both ways.

Even so, I am going for not spending hundreds on a valve, and not putting my anti siphons 3 ft in the air (ugly). I'm just betting that no dumbass code police cares about a single homeowner.

Let me know what you decided!

    Bookmark   May 4, 2011 at 9:12PM
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Maybe you should look at the problem from a different point of view. The water that siphons back because a line breaks and the pressure drops is going back into your house and eventually, if not repaired right away, to your neighbors houses. You will be drinking water with animal fecal coliform bacteria(ugly) and so will your neighbors. That is why there are regulations for this problem. Up to you. JMHO Aloha

    Bookmark   May 4, 2011 at 11:21PM
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