Extend a Stay Question

[Greg121]

Haven't found this addressed specifically, it may be obvious but... It seems looking at instructions videos etc with extend a stay and an external tank supply that it's assumed one tank is on and one is turned off. What happens if both are turned on?

[Deep Water D]

Then it will feed from the one with the highest pressure at the time. Which can change as the tanks cool, etc

[twinboat]

I remember installing my extend a stay and recall a one way check valve in the fitting that stays on the RV tank.
With that, no propane would flow into the mounted tank, even with both valves open.

The mounted tank should only be filled by the seperate fill valve, with the overfill valve in it.

There may be the same type of check valve in the fitting that connects to the portable tank. With that, gas can only flow to the RV system from either tank, both, if both valves are open.

[Greg121]

That's kinda what I figured. With both tanks option it would be like one bigger tank.