There are several grades of stainless steel, each having special qualities. 316 stainless steel is the highest quality grade available in custom water tanks. This grade of stainless steel has a chromium content of 16–18%, a nickel content of 10–14%, and a molybdenum content of 2–3%. The ideal grade of stainless steel for custom water tanks is 316; however, other grades can also be utilized, depending on the demands.