Where is my backflow device?

Anyone know where my backflow device might be? Sprinkler line splits from water main in third pic beside the sediment filter, then under the house. The 7 zone valves are split (3/4) between the back of the house and the side of the house.

Thanks for the help, I just bought the house and I’m trying to setup my yard right the first time!


You don’t have one because you are using anti-siphon irrigation valves, which work in a similar way, just using water pressure to prevent backflow and not a mechanical spring. Some cities allow these in place of a single backflow prior to the irrigation system, some don’t. As long as ALL the zones have these type you are fine.

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Anti siphon valves are typically installed by homeowners. Why don’t you install a Pressure Vacuum breaker backflow device? You will then remove the anti siphon valves, and replace with standard electric valves - installed underground in a valve box. The wireless flow sensor can be installed with the PVB as others have done on these threads.

Thank you for your reply @tmcgahey! Does that mean I can install the wireless flow sensor after the main cutoff valve coming from the street? (Picture 3)

I assume I would have to add 3 elbows and a 12-18" section of PVC to install the flow meter at.

@robertokc - I am not familiar with a Pressure Vacuum breaker but I will take a look at some other threads to see what you mean. Overall my goal would be to have the lowest cost installation possible, so if I can leave my anti siphon irrigation valves in place (they still work) that would be great.

PS - All zones have the Anti-siphon irrigation valves. I also plan to investigate where the pvc leads after the cutoff valve, if it goes under the house through the crawlspace I could potentially install the flow sensor there.

There are only two approved backflow devices that protect against high hazard cross connection (backflow). Pressure Vacuum Breaker and the Reduced Pressure Prinicipal assembly. Approval organizations include: International Plumbing Code; American Society of Sanitation Engineers; American Backflow Prevention Association; and the University of Southern California Foundation for Cross Connection. Irrigation systems are classified as high hazard for backflow that introduces E. Coli, other harmful microorganisms, pesticides and animal waste into your homes drinking water. Your home’s drinking water is not protected if you are using anti siphon valves.


In an effort to avoid starting a new thread, I have a Relay well pump that feeds my system, got the Rachio gen3 hooked up…

Do I have a backflow preventer? Flow meter mentions needing one?
Will adding flow sensor cause issues if using relay pump?