Question
I haven't been able to open the main shutoff valve for my sprinkler system.  It seems to be frozen stuck.  The valve is located about 4 feet underground and I've dug it out ready for replacement.  What is the easiest way to replce the valve ?  Do you recommend using a different kind of valve and/or location ?

Answer
You will have to make sure that the water supply is turned off at the source, or you will get very wet.  You will have to cut out the pipe on both sides of the valve, or at least one side and unscrew it from the other side.  I prefer to use gate valves, they are the most reliable.  Then you can use a coupling and a fitting called a slip-fix to put the pipe back together.