I have recently been asked to respond to a number of "yard sprinkler emergencies" in my area where pressurized lines burst or the primary side of the valve began leaking and then burst causing flooding.
It appears that three different circumstances apply here. First, the valves were not installed properly in the first place and always "leaked". So in time, moss and plant material grew around the leak and eventually caused it to burst. Second, Small trees or shrubs with major roots were planted over the sprinkler lines or right next to the valves which in time caused a break or failure. And third, shut off valves were not installed for the sprinkler system at all.
Here's my advice to anyone checking a sprinkler system in their yard.
Sprinkler valve installations are great for do it yourself types but I must stress the following. If you do it yourself, ALWAYS read and follow the manufacturers reccomendations for installation. Especially when it relates to preparation, types of glues and sealants and when to use pipe sealing tape(s). And always lay out, "dry fit" and " line in" ( mark all the parts where they join ) before you do any gluing. Once it's glued, it can-not be forced to fit if it's a bit off line.