If you buy a tank, get a copy of the test documents, or no deal. The fuel supplier may want it if they didn't provide (sell) you the tank. You may find they will at least negotiate a reduced price on the tank if you buy it from them. I am surprised you use so little. Most of my homeowners that are on propane use MUCH more.
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I do the things that I must, and really regret, are unfortunately necessary.

RIP OBG