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New Member


Thursday, January 12th 2017, 1:38pm

Heads above valve?

I bought older house with irrigation system, the valve (a foot above ground level) is watering a hedge which is higher then the valve approximately 10' (elevation wise) When the valve shuts off, the water in the lines from hedge appear to drain back down thru the valve. (surging) I had just replaced the valve with a anti siphon Orbit 3/4'' from Lowes. I thought the new valve was same as the old one, I don't remember the old valve doing that. should it have a backflow perventer in place or did the old valve hold it back? I know the box on valve says heads must be below valve.


Supreme Member

Posts: 5,294

Location: Metro NYC


Friday, January 13th 2017, 10:37am

You are describing a code violation, where the water supply is exposed to backflow contamination. An antisyphon valve works on gravity, so that is why they have the elevation requirement to be at a higher elevation than the heads that they feed.

When elevation is against you, it becomes your responsibility to correct the plumbing you described in one of several ways. The simplest way is to fit an RPZ backflow preventer into the supply, because one of them properly installed as per mfr instructions makes everything else not matter one little bit. However, the RPZ is expensive, and it takes away water pressure you might not be able to do without.

The other simple remedy is to alter the plumbing so that the valve you described gets a new location at the appropriate height. This means digging and adding pipe, but the added pipe is not a budget buster, and digging costs you only the shovel and/or pick to get the work done. This can also be worked by using a separate atmospheric vacuum breaker at the new location, and feeding it from the original valve location.


New Member


Saturday, January 14th 2017, 8:24am

OK that makes sense, so I could move the valve up to the ledge where the heads are (foot higher)....burying the control wire, up to that point.


Supreme Member

Posts: 482

Location: Houston, Texas


Saturday, January 14th 2017, 12:41pm

There is another option if you can do it that may be easier. Not sure if your coverage could handle the possibility of lowering the sprinkler heads to grade level by cutting the risers down and putting in male adapters and shrub adapters. It can sometimes be easier than digging up the area to relocate the backflow preventer.

But Wet Boots is 100 percent right.

Either lower the heads or raise the backfow preventer, or switch types of backflow preventers.

:thumbup: :thumbsup:
LI0006121, BPAT0011021, CI0009500


Active Member

Posts: 28

Location: NC


Monday, January 16th 2017, 3:55pm

I would steer away from the above ground Anti Siphon Valves.

Replace them with any standard electric control irrigation valve. You can Bury them
below grade in a valve box. These type of valves don't require any elevation
change due to heads afterwards being installed higher or lower.

You need to verify your backflow prevention device. Usually installed at the irrigation
point of connection (IE At or near the Water Meter) The Backflow device
is not electrically connected to your irrigation controller. It is a standalone valve
that protects you and the potable water supply lines.

Let us know what you find.
Licensed Plumbing & Irrigation Contractor


Supreme Member

Posts: 5,294

Location: Metro NYC


Tuesday, January 17th 2017, 7:43pm

I've been assuming this is a California system, since they are big on antisyphon valves.

Going further with this California assumption would have all the system plumbing be PVC pipe. This would allow maximum design flexibility in fixing the problem. Should the entire zone of heads be located at some uphill area, all fed from one pipe, the valve could be moved to the uphill location, as the OP mentioned, or an additional device, an atmospheric vacuum breaker, could be plumbed into that uphill location, leaving the original valve alone, which would save on wiring expense. This would still allow water to escape from the original ASV vacuum breaker when the zone shuts off, but that would by definition be potable water, and not contamination. {the antisyphon valve can be replaced with something else, that has no vacuum breaker to release water.

By the way, a photo or two of the system can greatly refine the advice given here.

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