Traditionally, the water lines in homes were made of copper. Today, many buyers have a choice. A popular alternative to copper is “PEX” which offers several benefits:
PEX water lines will expand if the water in them freezes and are less likely to burst than copper water lines that freeze;
PEX lines are typically direct to the end source (i.e., faucet) which can deliver hot water faster with less waste compared to multiple destinations splitting off a main line;
Because you have individual lines running to each destination, should there be a problem it is fairly easy to turn the water off to that specific destination; and PEX is simpler to install, meaning it may be less expensive than copper.