Why is it not advisable to use black steel piping for drinking water systems?

Using black steel piping for drinking water systems is not advisable primarily because it is prone to rusting. Black steel pipe is not coated with a protective layer like galvanized steel or plastic piping, which leaves it susceptible to corrosion when exposed to moisture. In a water system, especially when carrying drinking water, this rust can lead to contamination of the water supply, resulting in health risks for consumers.

Over time, as the inner surface of the black steel pipe corrodes, rust particles can dislodge and mix with the water, affecting its taste, color, and safety. The presence of rust can create an environment for bacterial growth and decrease the overall quality of the drinking water.

While other concerns such as weight, pressure handling, and cost may be relevant in other contexts, they do not have the same significant impact on health and safety that the potential for rusting does. Therefore, the correct reason against using black steel piping for drinking water systems is related to its corrosion properties and the subsequent risk of contamination.