Well this didn't work as well as I had hoped. One cycle was fine, pressure never exceeded 25#. However, the next time the heater came on the pressure was 0. It cycled the 9-64 (Burner blocked – Wait for blower to start) / 6-26 (Burner off - Factory supplied LWCO device or external limit is OPEN. Burner is off for 150 seconds, auto reset), which tells me it doesn't like the 0# pressure. I opened the fresh water valve, the pressure came up to 10 and the boiler came on. There are no leaks around the boiler or any of the radiators that I can see. Does this mean I have a leak somewhere?