Question
Robert, the shut-off valve to our sprinkler system is located next to our house and about four feet in the ground.  I use a key and a quarter turn to open it, but the pipe fills up with water after I do so.  How bad is this news and what does it mean?  Thanks.  

Answer
From what you have described it sounds like you have a curb stop or a ported ball valve. Some of those valves have a port that relieves water after you shut it off and I've seen those go bad and leak after you turn it on. It could also be a crack or something after the valve. The best solution is to dig down and see what you find. You might have to dig a wide hole so you have room to work on the valve. Part will probably be inexpensive but a lot of labor.