Air in LP gas line.

Thomas/NH wrote:
As a licensed gas technician, the gas doesn't drain out. You don't need to purge the line. It's a matter of pressure and once it restored, the appliance will light right back up. What small amount of air that you let in during change-over will be absorbed and pass through the burner as a yellow flame.

Slowly turn the tank valve back on so you don't stick the regulator.

THANK YOU.. (I said as much about the gas lines up thread but unlike you I'm not certified in this field. so Thanks for the professional support).

Question.. The pigtail that connects to the tank, does it contain a check valve or other valve.> Else I would think that Browian motion of the gas and air would let a little air enter, Not, likely, enough to make a difference, but there would be some exchange.. I know there are check valves farther in but as I said, in around 20 years of growing up with Propane.. I never had to re-light a water heater due to a bottle change less we ran out completly. And then it was the standard pain in the arse to re-light as if I'd turned it off at the control.