Draining Anti-Siphon Devices

We manage water systems which need to be drained for the winter. Once we installed anti siphon devices all the lines do not get drained and many freeze.

How do you do you drain a system with anti-siphon devices?

Thanks, Tom

If your talking underground sprinklers, I’ve had guys come over with 50 to 150 cfm compressors and blow the system out with air by slowly increasing pressure slightly until all the air is out zone by zone. They hook up to the tap on the supply side and close the valve going back toward the basement where it is set up to gravity drain back inside to a boiler drain type valve into a bucket…maybe a gallon or two, depending on the length of pipe to the out side.

I can’t post a picture in this thread of the forum but you can copy and paste this into your url window: http://www.supplyhouse.com/Watts-0388001-3-4-800M4QT-Anti-Siphon-Pressure-Vacuum-Breaker?gclid=CNu-g9nMrr4CFdSMMgodYUkA-A
to see a valve like I am referring to.

Water will go out. It just won’t come back in.