I've read a few articles about plastic pipes recently, and it seems the general consensus seems to be that all plastic pipes leech some amount of material into the water - however whether that's at a level that is bad for us is as yet unknown.<p>Before PEX, copper was king for house water pipes. It's still used a lot, but the main argument for not using it is labour costs - PEX is flexible, copper needs skill to bend it. However copper also leeches into water! But copper is an essential nutrient, so it may actually be beneficial, but at high levels it is toxic.