Propane...

Leave both open , watch the red 'green , tanks will last a long time , When gauge turns red you are then running on a fresh tank . Look at gauge every 2 or 3 days . Only a real dummy will run out !

Tiger4x4RV wrote:
When we had a huge propane tank for the house, we would go out and throw a bucket of hot water over it, then run hands down the side of the tank. The empty top part of the tank was warm, the part with the liquid propane in it was cold. Primitive, but it worked.

They make temperature color-changing stickers to apply to the tank that work similar, a little more visual, but still pretty primitive.

I do how Iraqvet05 suggests, I leave one tank closed, when first one runs out, I know I still have a full reserve and manually open the 2nd one, and then I have plenty of time to go get the other one filled.

When we had a huge propane tank for the house, we would go out and throw a bucket of hot water over it, then run hands down the side of the tank. The empty top part of the tank was warm, the part with the liquid propane in it was cold. Primitive, but it worked.

How large are the tanks? I have dual 30 lb tanks and never had to fill one after the first season. I'd suggest just opening one tank then let it run out completely that way you know you have a full reserve. The easiest and most reliable way to determine the level in the tanks are to lift them...you can tell by the weight when you are getting close to empty. Don't buy those stick-on gauges, they are junk.

Watch the RED/GREEN indicator.......
When Green turns to RED then 'in service cylinder' is now empty (that would be the one lever is pointing to) and auto swap reg has changed over to other cylinder

Flip lever to other cylinder.....RED goes GREEN

Remove empty cylinder and go get it filled.

Repeat when Green goes RED...cylinder is empty...swap get MT one filled