My attic is always hot. Why not pipe the water to a water heater in the attic? Why would the builder put it in a cool basement?
Before central heating, houses were built to take advantage of whatever natural heating or cooling that could be found. Now, they don't. I've visited old houses out in the desert that have sat unused for decades. They do not have any sort of air conditioning, and as long as they still have a roof they are still cool. Today's house, without air conditioning, would be an uncomfortable oven. The builders of the abandoned houses in the desert used the materials nearby, and built small houses. Today, people do not want small houses and builders do not want to purchase a bunch of adobe. Simply put, they don't heat your water like that because you can heat the water with a water heater now, and it is cheaper to put it down in the basement than set up a system to heat the water in the basement (for safety reasons) when it is cold and use water heated in the attic when it is hot. So, they have no incentive to do it any other way.
