I just bought a new home not long ago and it came with a solar water heater. I know absolutely nothing about solar water heaters. The tank looks old and rusty but the panels on the roof don't look to be in bad shape. The water seems to be heating ok but this morning there was no hot water. I don't know it takes awhile for hot water to return into the tank, or there is something wrong with the tank its self. I am thinking about replacing the tank because it looks rusted and in need of a replacement. How much would a new solar tank cost? does it need to be a special solar specific tank, or could i get a regular tank from Home Depot? Thanks.