I live in Colorado, it's quite dry here and can be quite warm in the middle of winter. If I blow out my sprinklers before the first freeze and don't water again until after the last freeze of the spring my lawn will be dead (edit: not really dead, but damaged, in much worse condition than neighbors). So I drag a hose and sprinkler out several times in late fall/early winter and also again in the spring.
In the spring, would it be safe to just turn the system on earlier and just drain the backflow preventer if a freeze is incoming, since the buried lines are less likely to freeze?
I'd love a system that didn't require winterization, but don't think that exists.
Best Answer
Yes, this can be a very viable option if the temperatures will not be near or below freezing for very long. This is how I've done it in Texas, where it rarely gets in the 30s, and never had a problem. For one or two nights, the bigger concern is a cold wind rather than temperatures in the upper-20s or low-30s.
I, and all my neighbors, would close the shutoff valves at the backflow preventer and drain it, wrap some pipe insulation around the inlet-side PVC pipe (maybe wrap an old towel or something around the backflow preventer itself when a hard freeze was predicted), and that was pretty much it for winterization. Nobody would drain any of the system past the backflow preventer, as that tends to mostly drain on it's own.
As long as the temperature during the day is above freezing, and you're not having multiple nights of freezing temperatures in a row, you shouldn't have a problem with your plan. Just make sure to wrap any exposed pipes with insulation, and possibly wrap the backflow preventer as well. Make sure you've had at least a few warm days (and nights) before turning the irrigation on for the first time, too.
Some notes, as installations may differ between areas. Irrigation systems in my area are 3/4" or 1" schedule 40 PVC, typically buried about 8-12" down. If your installation differs dramatically from this, adjust accordingly