KD4UPL wrote:
I suspect you have an auto change over regulator. I don't know that I've seen an RV that didn't have one.
It should have a little lever labeled "service" and a red/green indicator.
The tank the service lever points two is the one you use. When it's empty the green indicator turns red and the regulator switches to the other tank. You can remove the empty tank, get it filled, put it back, and turn the service lever to the other side. Now, when that tank get's empty it will switch to the tank you just filled.
X2, my 86 had a switch over regulator, so as above assuming the service valve is pointing to the 1/3 full tank, that tank will empty and the full will stay full. Then the scenario above plays out.