Codes for your area may vary a bit but having the tank indoors is usually universally verboten. Flex is usually allowed, but not thru a wall or floor. Usually code requires black iron or in some cases the clad copper. I can back up my 100 gal cylinder by using 25# grill bottles if delivery is a problem, as was the case a couple of winters ago. The company did finally agree to give me a 40% fill provided I paid the delivery charge and the inflated prices. I have considered adding my own 100# cylinder as a back up, but have as yet to check out my contract.
