Sprinkler System Backflow From Elevation Change

[Nessism1]

I just finished installing a two-zone sprinkler system in my backyard. One zone has a small section that's at a higher elevation than the control valves. I did a brief test before filling the trenches to check for leaks, and when I shut off the valve, water flowed from the anti-siphon/backflow prevention portion of the control valve.

I'm thinking about installing a secondary Pressure Vacuum Breaker valve in the system to further protect the potable water supply, but that won't stop the water from backflowing out of the valve every time the system is used. Replumbing the system, elevating the valves, is an option, but an unsightly one, since the valves are on my patio. I built a box to protect the valves, and that work looks for naught at this point.

Open to suggestions.

 

[Lawnman23]

I am not a plumber, just looking at the setup but why not just install a one-way check valve between the control valves and the supply side? It would require redoing some of your nice work but would still fit under the box when done.

Something like this for instance.

 

[alarmguy]

Have you ever lost water service at your house?
If not, I wouldn’t be concerned, however @lawnmans suggestion should put you at ease

 

[Nessism1]

I am not a plumber, just looking at the setup but why not just install a one-way check valve between the control valves and the supply side? It would require redoing some of your nice work but would still fit under the box when done.

Something like this for instance.

I've been considering this approach. I can put the valve anywhere in the system. It's a bandaid fix, though. With hindsight, I should have used a high-mount Pressure Vacuum Breaker valve, then instead of the valves I chose, I could use simple solenoid valves. It's the vacuum breaker that's attached to the solenoid valves that I have that are puking.

 

[Nessism1]

Research suggests that check valves are not the ideal solution. Guess I need to redo the plumbing. I'm going to order a proper Pressure Vacuum Breaker valve, elevate that 12" above the highest sprinkler head, and then use simple solenoid valves to control the sprinkler system. Removing the solenoid valves with integrated vacuum breakers. Kind of frustrating, but the plumbing will be simple enough. The valves can go under my box, but the PVB will stick up a couple of feet.