this fall i have plans on building a solar pre heat tank for hot water. rising gas costs are forceing me to look into alternative energy. ive already switched to wood burning heat in home and shop. and im gonna install electric registers or solar registers to replace the back up furnace that we rarly use. but heres my main objective this fall. take a 40 gallon tank. its painted black and wrapped with black copper pipe. installed in a box also black and fixed with glass front and top. it is hooked into the main water inlet. then to reg water heater. wich im going back to electric after switching to propane 2 years ago. what it does. sun or solar heat heats up water in the exterior tank to 120-160 degrees depending on the time of year temp. even in winter. then your water heater witch is set at normal heat keeps water warm like normal. BUT. as you use hot water instead of cold water going in from ground your pulling hot water from the preheat tank heated for free by the ever burning sun. THUS your water heater doesnt have to heat it. or if it does it needs much less heat. reducing greatly your energy consumption. saving money for other needs. one man one step to a fule free life.