Particularly in areas where potable water is not easily accessible, water is sometimes collected from roofing and used for cleaning, bathing, and even drinking. In many cases, property owners who are using their roofs for water collection often turn to metal roofing because it has a surface that is smooth and stays clean.
There could be health concerns associated with doing this.
Before metal is painted, it is cleaned and receives a pre-treat process. A component of the pre-treat is often chromium. Although the chromium is subject to a clear rinse and then the two-coat paint system is applied on top of that, paint manufacturers and coil coaters still warn that a minute amount of chromium could surface through the paint. Therefore, they cannot recommend the use of painted metal roofing for catchment of drinking water. Additionally, there may be other risks associated with drinking rainwater, based upon local environmental conditions.