I have a small 4-zone system at my house. My property is about 100 feet deep and 50 feet wide so the sprinkler system does not really cover much land. The system has a Wilkins Model 420 Pressure Vacuum Breaker right where the main water line comes out of the house before it goes to the four zone valves. There is a drain plug in the main water line outside the house that sits right below the Wilkins breaker. This drain plug is where the pressure tap is connected to blow out the system.
I have a Sears 5.5 HP 25 gallon compressor that is rated at 8.6 CFM @ 40 PSI and 6.4 CFM @ 90 PSI. I have 50 feet of 3/8 copper tubing in a coil at the output of my compressor going to a water filter and a quick release fitting. I ran 75 feet of ½" rubber air hose (after the 50-ft copper coil) out to the drain plug below my Wilkins breaker. I filled my compressor, turned on one zone of my sprinkler and set turned my compressor regulator to 50 PSI of output. I heard a lot of "gurgling" at the Wilkins breaker but my sprinkler heads did not pop up. I raised the pressure a bit to 70 PSI but the sprinkler heads still did not pop up. I had a similar problem last year but after a while of experimenting I got the sprinkler heads to pop at 50 PSI and the "gurgling" went away. I am not sure how I got it to work last year but I cannot get it to work again this year.
Does anyone have any ideas what the problem might be? Is it possible that my compressor is not flowing enough CFM? Would it help if I pulled my compressor out of garage and put it near the sprinkler drain plug and used a much shorter rubber airline to hook up my pressure tap?