Final answer:
Cast-iron fittings used in potable water piping systems up to and including two inches in size should be galvanized to prevent corrosion and ensure water quality, in accordance with plumbing codes.
Step-by-step explanation:
Cast-iron fittings, up to and including two inches in size, when used in connection with potable water piping, shall be galvanized. This is required to prevent corrosion and ensure the long-term integrity of the piping system. The galvanization process involves coating the iron fittings with a protective layer of zinc, which acts as a barrier against moisture and oxygen, two elements that cause iron to rust. It's important to use galvanized fittings for potable water to ensure water quality and prevent contamination. Furthermore, national and local plumbing codes often specify the need for galvanization in potable water systems to promote public health and safety.