Here is what happened. I was trying to use my 6Gal, 0.8HP, 135psi compressor to blowout my sprinkler system. The first zone which had just 2 mini sprayers worked fine and all the water gushed out. I tried to remove the compressor hose in order to stop the zone 1. Reconnected the hose and opened zone 2 (the pop up sprinkler heads), the sprinkler heads did not pop up at all and there was some minor noise from the PVB(Pressure Vacuum Breaker). To troubleshoot I opened the PVB top to expose the springs and other parts, noted that not enough air coming into the PVB. After I unscrewed the thingy that sticks out the PVB where we connect the compressor hose, found there was some white plastic thing that somehow got into the nozzle. i.e., from inside of the PVB it got into the small valve(which we turn with screwdriver). After clearing that out, the air started coming out with full pressure from that valve. I put the thing back and also put the PVB parts properly (saw the YouTube video from Watts). Now when I connect the compressor hose, there is a extremely loud noise from the PVB and no water blow out happening. What is going on? Should I reduce the air pressure CFM ? I have no idea what to do now.