A 5lb. tank suits our needs (2 people) fine so far. It's basically just for cooking now although we have run the furnace for a few hr's too. . We have 15 nights on it since the last refill and it's still about half full. I use an inline gauge with it.
I mounted it and a utility / battery box on the tongue of our trailer. I installed a receiver tube under the box on either side. I currently have the propane cylinder on one side and a water tank on the other. I will be adding an onboard water tank and an on demand water heater to the trailer. At that point I will likely add a second 5lb. tank on the tongue.
The tank sits on a metal disc with a rubber pad that I welded to a square tube and that goes in to the receiver tube. It is also attached to the box by a welding tank strap.
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