Convert the propane hot water to electric with this Hot Water Hybrid Heat Kit. You will still have access to the propane hot water, but with this kit you can simply use electricity instead of propane and have 24/7 hot water. It's silent too, no loud whoosh when the propane is burning like crazy. It's only 400 watts, comes with outstanding instructions and a regular 3 prong electric plug.
The 400 watts is plenty, I set mine on the highest thermostat setting so I would have plenty of hot water. They ship it with the thermostat set pretty low, so crank it up to the max if you prefer. It comes with an on/off switch that I rarely used as I pretty much left mine on 24/7. Even if you drain it all out cold, it took mine about 15 minutes to recover in balmy weather and longer in colder weather (colder water!)
https://www.amazon.com/gp/product/B0024ECCJW
They sell a kit for 6 gallon and 10 gallon heaters.
I did my own installation and the directions truly were super with clear step by step diagrams, pics and written details in plain English. I used mine for 7 years with no issues, then sold the rig with it still working. So overall it was a cheap sound investment I thoroughly enjoyed.
Someone else will be along to solve your propane issue, if you still want a spare tank.
