PVB's and blowing out a system.

[wwsmith]

So I sat in my driveway this past weekend having a beer with my neighbor while we watched some folks he hired finish up connecting up his new sprinkler system. Here it is required by code to have a backflow preventer installed on the main line feeding the manifolds regardless of whether you use anti siphon valves or not. So he has 3/4" Pex run through is basement which then transitions to 3/4" copper just before going through the wall to the outside where it then 90's up to connect to a Pressure Vacuum Breaker about 2 feet from the ground and then back down in PVC to the manifolds. There is a ball valve in the basement to shut off water on that line as well in the winter time to allow him to blow out the system.

They put a fitting in just before the PVB to allow my neighbor to connect a blow out connection to so he can blow out his lines when ready to winterize. Now comes my question (finally!). Is it ok for that blow out fitting to be put before the PVB? Obviously I don't know anything about them so I guess out of personal curiousity I wondered if it was ok to blow compressed air through the PVB? There is also a drain installed in the basement over the sump pit so he can blow out the lines both ways. But I wondered if he might not be setting himself for trouble come this winter by blowing some 30 or 40PSI through his PVB or is not a problem? Mine is located after my PVB so maybe I am just basing my assumption on what I am used to seeing? :confused:

[Aaron91]

I have a hard time picturing this somewhat. Pictures are always helpful. I would not personally blow air through a Back Flow Preventer. I always install a valve before and after my devices because they require two. I would turn the valve after the back flow off, and then have a connection to blow out the line, which would be from the valve after the device out to the irrigation system. I hope this helps ya and makes sense!