Nonmetallic pipes must be installed in which locations according to the code?

The requirement for nonmetallic pipes primarily stems from their susceptibility to environmental exposure and potential damage. When installed outside, particularly underground, nonmetallic pipes are often subject to specific conditions that necessitate their use, such as resistance to certain chemicals found in soil or moisture considerations.

Underground installation typically requires the pipes to be protected from physical damage and environmental conditions that could compromise their integrity. Nonmetallic piping materials, such as PVC, are preferred in these situations due to their flexibility, corrosion resistance, and generally lower installation costs compared to metal counterparts.

While there are specific guidelines for where nonmetallic pipes should be installed, including within buildings or above ground, the unique advantages and code specifications for outdoor installations often highlight their usage in underground settings. In this scenario, understanding the application and performance characteristics of nonmetallic materials helps clarify why this installation method is emphasized by the code.