Connecting pex to copper?

Hi everyone. I am adding a basement bathroom and have a question about running the new supply lines. The main floor bathroom is directly above so I have good access to the existing copper. Initially, I had planned to just T off with new copper. After reading a little about Pex I thought it would be so much easier to run Pex lines off the existing copper rather than build up the necessary maze of new copper lines. Does this sound like it makes sense? Are there special fittings to join Pex to copper lines? I could solder all the copper together if I have to. It just sounds so much easier to run flexible plastic lines. Thanks for any advice.

The best brand of PEX is rumored to be Wirsbo, which uses expansion style fittings. I'm not sure if they make an adapter to go from copper to PEX or no. The crimp style fittings have an adapter. I would not use any of the push style or compression stye fittings. Use either the Wirsbo expansion fittings with the correct tools or the crimp style fittings with the correct tools. Many of the crimp style fittings have a crimp they call qickclamp this is not an automotive style clamp, never use those. They are a crimp that one tool does several sizes.

Zurn has a law suit against it for their brass crimp style fittings breaking due to some water conditions and the foriegn fittings not holding up. I use Zurn because the corperate office is closer to home, but I have been unable to get a response from them about the suit. Kitec is another brand that is having legal issues. The pipe all seems good as long as you stay away from the al types and go straight plastic. My advice is make the fittings accessable, they seem to be the issue. Copper can have issues too, so it is not perfect, in my opinion PEX is the best thing going now, just don't put fittings in the wall and don't put the pipe ot fittings in a bind, allow a lot of room for expansion and contraction.

Go to Zurn's website they have a really good how to on the crimp style fittings and installation.

Wirsbo (Uponor) has fittings that are PEX x Copper

For that matter, all PEX piping will have transitions to copper, and for threaded.

Thanks for the replies. I'll head on down to the plumbing supply shop to see what they have.

One more question. When I tap into existing lines to feed the new lines are there any concerns about where or how many times I can T off of existing lines? In my case I was planning to cut into the hot and cold supplies before they reach the sink and toilet on the main floor. I would then need to run new hot and cold to the new shower and sink and a cold line for the new toilet. Should I just cut into the existing line once and keep adding T's? Or should I cut into the existing line (e.g. the cold line) three times and run lines directly to the fixture? Or does it matter? Any advice would be appreciated.

edit: I'll just start a new thread for this question.

I have used both expansion joints, crimp-on joints and push-on joints on PEX. All have performed to my satisfaction.