While I do not live in the Tucson area I do live in west Texas. Our "cold" water gets warm enough in the summer that you can take a shower without using any hot water and it's all underground. So you might not be getting what you want. I think an above ground tank in a well house might be something to consider. Be able to inspect the tank regularly and hey, you can AC it too, lol. Looking at a 2500 gallon tank, it appears they are about 9 foot in diameter and 7 foot tall. So not even a big building is needed.