SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

Hey all. I live in the warm climate of North Carolina, and have never winterized my system before. This year I upgraded my heads to the Rainbird 5000 series with the SAM feature to prevent leakage down to the low spot of my zones. I replaced them all and now my system works great with no air in it at all. We don't get severe cold for any long periods, but there will be a few days below freezing. I'm worried that since these heads are designed to keep water from flowing back out of them that they'll all be filled with water all winter and susceptible to freezing. Any thoughts/suggestions would be appreciated. Thanks!