# What adapter do I need to blow out my sprinkler system, and where does it go?



## ryeguy (Sep 28, 2017)

The water comes from the top of the pic. There is a valve above there to shut it off. The backflow preventer is outside on the other side of this wall. The smaller pipe that drains into the laundry tub is not threaded, so I'm unsure if I can plug in there or not.










Here's the backflow preventer. The valve on the right is threaded internally. It's bigger than a standard hose. It's also cracked on the backside (away from the camera), so opening it leaks out from there.










Is it possible to hook up to the pipe above the laundry tub? Or maybe one of the two little connectors on the backflow preventer? I had this winterized by a company years ago and they used an air compressor, but I don't remember where they plugged it in at.


----------



## NanserbE (Jun 29, 2018)

You'll want to plug your compressor into the bottom port on the backflow preventor I believe - someone else can chime in if I'm incorrect. I have only ever had double backflow preventors which look a lot different than yours.

It should be a 3/8" NPT thread, then you just need to adapt that to an air chuck and pressurize your system, open a zone, let it blow out, close the zone, re-pressurize, do another one, etc. Water only expands 10% when frozen so you don't need to get every last drop out. I personally do each zone twice and I haven't had issues.

You'll also probably want to drain that line from your backflow preventor where the water enters. I'm guessing that's what the valve above your sink in that picture is for to prevent it from freezing.


----------

