Reading a post regarding using a tempering tank to reduce water heating costs brought this topic to my mind: I have 50 vacuum solar water heating tubes. Just going on a low 350BTU/hr/tube I estimate a rise of ~25F/day for 1000 gallons of water. I plan on using the solar heated water for hydronic heating in a ~2000 sq ft habitat, for hot water needs, and "garden". I have made a prototype 4 tube assembly, but have not tested it to get a real number on the BTU's/tube. I plan to do that early next year. If there is an interest, I can post a pic of the prototype heat exchange assembly. Another related interest of mine is thin shell concrete. I have made small water tanks (~60gallons) and have built a jig to make 1000 gallon concrete water tanks. My thoughts were to have (~6 cisterns) with a range of temperatures so that over heated water doesn't become a problem. Since is still in an early phase and I am not tied to a timeline, I am interested in any comments from the members.

Yes, that is the right way to heat water. If you haven't already, be sure to visit the BuildItSolar.com website. Lots of similar projects and great information on that website. This will be a fun and rewarding project...good luck!

Thanks, sailawayrb,I will visit that site. Years ago I did, so I'll use it as a resource.