And blew out the lines. However, I accidentally connected it to the city side of the back flow preventer and I thought it odd when the sprinklers weren't blowing. Checked the pressure on my compressor and it was 35 psi. Then it dawned on me, I had the air compressor hooked up on the wrong connection. I reconnected the compressor to the distal side of the back flow preventer and it worked great and I blew out the lines.

So, to the problem (before I moved the air compressor to the correct connection)...my valve from my house central connection to the back flow preventer was closed (proximal to the air compressor) as was the valve just after the air compressor connection (distal). So, it was a closed system between the closed connection from the house and the closed connection on the intake side of the back flow preventer with the compressor in the middle.

Shouldn't my compressor gotten me closer to 100 psi, or was the 30 feet of PVC too long for it to pressurize?

Do I have a leak on that side of the system? I ask, because every spring and every winter when I go to turn the key, there is always and inch of dirt (in the spring) or mud (in the winter) in the tube when I turn the key on or off.

All of this is under my driveway...