I have found that the homeowners think it is the pressure that does this....ALMOST ALWAYS..they say "that new backflow valve you put in last spring exploded when I turned it on this spring"
Me: "Did you turn the system on after I winterized before today?"
Them: "NO...."
Me: "Really?"
Them: "Oh wait...I did turn it on back in February to water for about a week, but I turned it right back off"
Sigh.....
BSME is right....the freezed damage doesn't always show up when you look at it....then when you ratchet that first ball valve open as fast as you can...hint

....it blows the already cracked and disconnected parts pretty high and it is VERY dangerous"
Sprinkler Solutions, Inc.
Arizona and Colorado
www.sprinklersolutions.net