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

I just spoke with the tech department at one of our suppliers. They came up with a few scenarios.
1. If the bottom of the valve sets down in the soil and the ice is basically from mid-body up then they don't think the pressure is enough to do damage.
2. If the valve is indeed elevated and ice completely surrounds it they can see some pressure problems but no way to predict. The pressure still isn't that great and there is a chance no harm was done. That will be a 'turn on and watch' scenario.

3. This is our main worry. The bleed screws on valves are course thread and not completely waterproof by design. If the screw was opened to blow out the system and then not turned completely closed rain/snow water could be anywhere from just along the screw threads to in the valve body. In this situation the freeze could damage the bleed screw/thread or, if enough leaked into the body, damaged the valve itself. In this case you are rebuilding/replacing the valve. Again, have to turn it on and watch for problems.

The manifold, if well made, seems to be the least of the worries. With no water inside it should be fine. However, the colder it got the more brittle it got; pressures were low but someone could have stepped on it, cracking a line. Check visually for cracks first.

How to minimize damage? No good answers but some advice. Make sure everything is completely defrosted before you test anything. Don't use a heat source do thaw it out; you don't want hot spots or missed areas. Just let it melt. Once melted see if the bleed screws are closed. This will give you a little warning of potential problems. Make sure to close them if open.

Now you just turn it on and hope for a good day.

All that being said, the general feeling is that no damage was done and things will work fine.
There is just no way to be sure at this time.

If you don't mind, come back and let us know what happens. My curiosity is killing me.

Pretty common occurrance in the snow belt. Is it good for the valves, probably not. Is there anything you can do to prevent it, probably not. The majority of todays professional grade products have made serious advancements in quality to allow for most climates. Northern Minnesota's climate is hard on sprinkler components, and most people tolerate it.
I can tell you, though, valves are usually the last component of a sprinkler system affected by freezing, both internally and externally. I've started systems in early spring, in which, only half the valves would open due to frozen valves. Gave the same advice as above, let them unthaw and check their performance. I think you'll be surprised as to the punishment they can withstand.