Hi 1231ChaseB,
I believe it's a safety issue. The doorside tank output is routed across the RV, underneath your living quarters. You don't want high-pressure propane routed through an unventilated area under living quarters. Having a regulator at the tank drops the pressure before the propane goes across the RV.
I think to eliminate the regulator, you'd have to replace the hose with iron pipe.
I've wondered what the reason was for this regulator and this makes sense to me.
Our current problem makes me wonder if this regulator is starting to fail.
We have a device that alerts us to an empty LP Tank. It's a switch that sits on top of the main regulator. This switch is triggered by the "pop up" flag that turns red when one tank is empty. When the flag pops up it sends a signal to our inside box and an led begins to flash.
Lately, when we use the furnace or oven, this device lights indicating an empty off door side tank. When I check the tank, it's not empty. When we turn off the stove or furnace, the light goes out, back to "normal". The pop up on the main regulator stays in the green.
I've tried switching tanks side to side and the same situation occurs. I'm wondering if the door side regulator is the culprit by not allowing enough propane to the other side.