wgriswold wrote:
The pressure varies with temperature. At 30 deg F it is about 50 psi and at 100 deg it is about 180 psi.
that's at the propane temp, not necessarily ambient since the propane temp drops as it boils at about -40F as you draw off the vapor. So tank pressure varies all over the map depending on draw rate, temps etc. The tank will vent if pressures get to high, but don't know what that pressure is.
One reason for using a two stage regulator is to get a more constant outlet pressure over the wide variation of tank pressure. First stage regulates to an intermediate pressure, the second stage then regulates down to the final roughly 1/2 psi.