which side of backflow value

[Deodiaus]

I have this backflow value in my back yard.

am trying to winterize my irrigation system. Does anyone know which side of this valve do I shut off the valve? I turned the spigot on the side with the metal piping assuming that the PVC piping side went out to the yard (and the spigot on that side is in line with the piping). Where do I insert the compressed air to get rid of the trapped water? On the far side, I think I see three places where I can attach the air supply. Does anyone know of a website with nice pictures of how to do this?

[DD_BobK]

Who used to do this for you? (for the previous owner?) Call them out & have them show you. If you dont do it properly the unit will freeze and be destroyed.

My caretaker did it wrong one year and the unit froze and the main casting broke.

cheers Bob

[ransley]

I remove mine since ive been told it will freeze from remaining water and be ruined, my valve was about 300$, its hard to tell from the dark photo but it doesnt look like yours has easy to remove flanges or that it has been removed anualy. On my ball valves the sprinkler guy left them not fully open or closed saying that could trap water and crack the casing, he left them in the middle after blowing it out. Some systems are designed to not need blowing out. I would use the person the previous owner used to first know the system.

[Jules]

I'm glad I'm not the only one who keeps making that typo :-)

Isn't that a flow direction arrow on the valve body, bottom-right? That'd make the PVC side the inlet and the metal pipe side the outlet.