I have to agree with Hal on this one. I once lived in a house with well water that was very corrosive to the copper pipes. The house was plumbed properly with type L copper (the blue stuff) and we had all sorts of pinhole leaks just as described above. We used to have some feeder thing on the main line that looked like a water filter but we had to put these crystals in there and it was supposed to slow down the process of corrosion. I was maybe 15 or 16 at the time so my memory may not be exactly accurate, but I think it was called a phosphate feeder? Anyway, yes type M (the thinwall red stuff) is supposed to be for hydronic heating ONLY, and type L for regular potable water. Type M is significantly cheaper, so there is a definite temptation to use it. Around here the inspector would instantly fail a house with type M used for domestic water. The pex is a great way to go. There are many less fittings required, and there's no risk of burning your house down by soldering with a torch in tight quarters. There are two main ways of attaching pex to the fittings, Crimp rings and plastic sleeves. The crimp rings require a minimal investment of 50-70 bucks in the special crimper pliers, but have the downside of being steel rings that could possibly corrode over time. Doubtful, but possible. The plastic sleeves require an expander tool which is a cordless motorized thing thats several hundred bucks, but makes MUCH better connections. Needless to say, I'm poor and own the crimpers. I also have the pex cutter that was mentioned and it does come in handy for many plastic things that I need to cut.