Which type of pipe is not recommended for potable water distribution?

Polybutylene is not recommended for potable water distribution due to its susceptibility to degradation when exposed to certain conditions, including chlorine and UV light. Over time, this can lead to leaks and potential contamination of the water supply. The material was widely used in plumbing systems in the past, but concerns about its reliability and safety for carrying drinking water have led to restrictions and recommendations against its use in new installations. In contrast, copper, PVC, and PEX are commonly accepted materials for potable water distribution and have proven to be safe and durable when used properly.