Question
I opened the main valve to my sprikler system yesterday and water flowed from the valve.  I live in Utah and the valve is about 4 feet underground and access via a 2 inch tube.  The tube filled up and continued to flow for over 30 minutes.  I decided then to switch off the valve and the water stopped flowing.  While the valve was open (and leaking) I tested the sprinklers and they seemed to be getting adequate pressure.  Any suggestions?  Thank you in advance.

Answer
Hey Bob, I hope this helps. I would imagine, the type of valve you're talking about, is called a stop and waste valve. Do you use a key with a single slot in it to turn it off or on and also it should only turn about a 1/2 a turn. Well if this is the case, let me explain how this valve works. In the winter when you turn this valve off, there is a little hole in the side of the valve, and any water in the pipe running to the sprinkler system, will drain out this hole. When you turn it back on, the water should flow to the sprinkling system, but this hole will seal from the valve being turned on. It sounds as if the seat that seals this hole might be worn out. What you might try, is to make sure when you turn it back on, that it is fully on. If the valve is only partially on, then the water will still drain out of this hole. When you turn the valve on counter clockwise, it should have a definite stop feel to it. You might just want to monkey with the valve back and forth, to see if you can get it to seat right. Let me know if I can help you out anymore, thanks and have a great day.