Make sure the single main valve in the cabinet is at the 12 oclock position or all the way open. Then be sure on your remote valves that at least on (the deepest) is all the way open when you start it. If the pop off valve still opens and the gage goes to 30 there is a restriction some where else.If all 3 remote valves are all the way open (for this test)does it still do this, try it and let me know.
