In another thread, dole valves and water pressure were discussed in an open loop system. I'm also hoping to keep my old WF going for at least 2 years, then take advantage of the tax credit. My 2 stage Premier is plumbed exactly like the diagram in the install manual, 2 solenoid valves with 6GPM flow valve on 1st stage, 5GPM valve on 2nd stage. The system is supplied from our home well pump, with a pressure regulator between tank and furnace set at 20 PSI. It's noisy! I've read about systems running at full system pressure, and others with regulators, the manual really doesn't address this, it only mentions flow. What kind of pressure should an open loop system see? And in the future, would a new furnace with built in flow control get full pressure or something regulated?