garyemunson wrote:
The Lp tank is certainly aged out. Being rusty is an additional death sentence. You should replace it. You are likely to encounter places that will not fill it, generally happens when you REALLY need LP. If it were not rusty, you could probably get it recertified but a new one is really the way to go.
If it's a portable DOT cylinder, along the lines of what one uses for a backyard grill, this is excellent advice. It's not improbable that the old cylinders also don't have the OPD valves that are required in all but a few specialized cases now for cylinders.
If it's a built-in ASME tank, it takes a lot of rust to render it unsafe as they are much more heavily built. Usually if it's just surface rust all that is required is to clean and repaint. A propane shop (a full-service one, such as AmeriGas or others that rent tanks and have trucks to fill them and so forth) could likely give you specific advice if needed, and help with any parts that need replacement. ASME tanks do not "age out" or need periodic recertification, though shops may reasonably refuse to refill one that is in poor enough shape due to safety concerns.
I would generally expect a motorhome to have a permanent ASME tank rather than cylinders, but either one is certainly possible.