Plastic may not be so bad. There’s a research group that has studied various pipe materials. The result generally seems to be that PEX varies widely but leaches detectable and smelly things. PVC does too. CPVC doesn’t seem to affect taste/smell or to leach much. PP-R is also pretty good. Copper, somewhat surprisingly (to me) affects taste. I haven’t seen niche materials like silicone or PTFE tested.
