I'm about to install two direct vent propane wall mount heaters to continue my overall conversion from oil to propane. Anyway, the instructions for the heater specify the location to run the gas line through the wall, but that doesn't leave room for a shutoff valve; it's very close to the gas inlet on the heater. Can't see that the precise location matters, but is there a required location for the shutoff valve? Does the valve have to be indoors, or can it be on the outside of the wall? Is it a code thing?