Recommended plumbing pipe material for ADU?

[Bruce P.]

Hi,

My friend is building a ~600 sq ft ADU in So Cal/Los Angeles and is wondering what type of pipe might be best from a quality/maintenance/cost standpoint within the interior of the ADU (I realize that the line connecting the ADU to the sewer line might be HDPE or some other plastic pipe...)? Apparently there are five basic types of plumbing pipes per this article with copper being fairly common.