# Blowing out System



## jeffzee (Apr 16, 2018)

Hello everyone. Moved into a new to us house this summer, and it has a built in irrigation system. This is the first time i have had such a system, sure is wonderful! My question is blowing it out for winter. I have watched several videos on the matter and i understand the principals. My question is hooking up my compressor to my system in particular. From what i have watched and read, it seems i do not want to hook the air up before the back flow preventer. The odd part is, the installer T'd in a hose bib between the main (exterior) valve and the back flow preventer. This would sure be an easy place to hook my air up to, but is that definite no no? I guess my other option is to hook up to the last port on the back flow valve itself? Ill attach a pic, hopefully it works. You should be able to see the main valve at one end, then the T'd hose bib then the back flow valve. I appreciate your thoughts!


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## chrismar (May 25, 2017)

Mine is setup similarly, and I hook up my compressor to the hose bibb off the tee. I was always under the impression you did want to be behind the backflow, as to rid the water from it as well. In any case, I've never had a problem blowing it out this way (3 seasons so far).


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## skitzo420 (Oct 24, 2018)

How can I do it myself at home?


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## Delmarva Keith (May 12, 2018)

Your installation is a little jacked up. You don't want to connect a compressor behind the backflow. Compressed air is basically never just "air." Whatever crap is in the air lines or any oil blowby from the compressor crankcase is in there too. You also don't want to blow into the far test port because that can damage the backflow and anything that gets into the backflow presents the same contamination issue as blowing through the backflow.

The "right" way to do it is to isolate the backflow by closing the far ball valve before blowing into a T past the backflow. After blowing out the system, reopen the backflow ball valves so the backflow can drain whatever little water remains in it into the lines. To do that, you'd have to add another valve box with a T and plug past the backflow.


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