What type of piping is allowed for use with hot water heaters or boilers?

The use of CPVC (Chlorinated Polyvinyl Chloride) or PEX (cross-linked Polyethylene) piping for hot water heaters or boilers is appropriate because these materials are designed to withstand the temperatures and pressures associated with hot water systems. CPVC can handle higher temperatures than regular PVC, making it suitable for hot water applications. PEX offers flexibility and resistance to scaling and chlorine, making it ideal for both hot and cold water distribution, as well as for heating systems.

In contrast, using only PVC piping is not advisable as standard PVC isn't rated for high temperatures, which can lead to failure in systems that require hot water. While metal piping is durable, it is not the only option available, as it can be subject to corrosion and other issues over time. The option of "any type of piping" is also misleading, as the materials used must be specifically approved for the application to ensure safety and compliance with plumbing codes.