Installed outside in the harshest sunlight, tucked away in the dampest, darkest corner of the basement, Challenger “I” series can take whatever is thrown at it. Its specially formulated two-part almond paint and epoxy undercoating offers the best defense possible against Mother Nature. “I” series Challenger tanks are built with a high quality stainless steel elbow and, like all of our well tanks, are equipped with our patented CAD-2 diaphragm technology.