I can supply a 360 gallon,
540 gallon, or larger solar mass storage tanks that you can get through a 24" door, or down stairs, that is designed for potable hot water, and they are less expensive than standard DHW tanks. I was getting lots of calls for retrofit solar heating using 10-12 collectors, that required at least 500 gallons, but the tank had to get inside the building. Our big German solar tanks do not often go into retrofit building.
