Question
I recently turned on my sprinkler system after the long cold winter.  I always turn off the valve between the meter and the system at the end of the summer.  This year when i checked the system, all the zones have very low pressure leading me to believe the problem is somewhere between the meter and the system.  What steps can I take to check things before I start digging?  Usually when I turn on the main valve, I hear watter rushing through, this year nothing.  I tend to believe the pipe between the meter and the main valve is damaged but there is not evidence of this.  How can I check the main valve?

Answer
Thanks for the question.
My first thought would be look for any leaks in the system. You said long cold winter. Even a winterized system can get a pocket of water in it and freeze.
To check the water supply, I would suggest installing a pressure gauge in one of the backflow preventers test ports. The backflow is the first item in your system, near the meter, usually outside. Close the last valve of the backflow and turn on the water. You should have a minimum of 40PSI. Now turn on the valve at the backflow and watch the gauge. It will initially drop the rise up to the original pressure. (assuming you have no leaks) Next, turn on a zone and watch. It should do the same thing, drop, then rise to a pressure within 6-10 PSI of the original pressure. If you have more than 10PSI loss, I would suspect the plumbing or the meter.
It is possible the valve has lost it's connection to the ball or gate which turn the water on and off. The only way I know of is to cut it out.
One other thought, try installing the gauge on the house water. Like a hose bibb. Then repeat the process. If you get low pressure on the house when the system is on, your not getting enough water from the city.

Matt