Are cast iron fittings permitted in outdoor piping?

Cast iron fittings are not permitted in outdoor piping primarily due to their susceptibility to rust and corrosion when exposed to environmental elements. Over time, moisture, temperature fluctuations, and other outdoor conditions can lead to the degradation of cast iron, which compromises the integrity and longevity of the piping system.

Using materials that are more resistant to corrosion, such as plastics, copper, or certain alloys, is advisable for outdoor plumbing applications to ensure a durable and reliable installation. The regulations typically reflect these practical considerations, aiming to promote safe and sustainable practices in plumbing.

The other choices suggest scenarios where cast iron might be allowed; however, the consensus in plumbing codes is focused on preventing potential hazards associated with the use of cast iron in outdoor settings.