Pex to Copper

I'm roughing in for some hw baseboard. I have been using pex (w/O2 barrier) and it's been working great as this is a remodel. When roughing in stud spaces, can I install a copper stub out elbow that is made for a pex conn on one end and a sweat conn on the other. After i've crimped on my pex, and the wall is rocked, I am concerned that my sweating on the fin tube will heat up and damage the pex.
In other words, what are the best fittings to use for this application.
Thanks in advance for your input.

You need to have more copper between the pex and where u are sweating. Either all sweating is done before the crimping or you must have something like 18" + of copper.

I'm sure the pros will know more specific numbers, but that's what I did when I ran mine. Just keep the pex as far a distance away from where you arw sweating.

I know they sell copper stub outs for sink stops that are nothing more than a little L pex crimp and then turn out the wall. I would imagine Unless you are putting a compression stop on there then there is very little to sweat to.

Makes sense, Thank You

PM to you...

Call your local plumbing whole-saler and see what they have. They may have exactly what you're looking for. Us plumbers use something similar quite a bit with bathroom rough-ins.

I call them pex bullets (Don't know the technical name for them) but what they are is a prefabbed copper 90 that have a pex crimp fitting on one end. They can also come with a backing plate on them so you can screw them to a stud.

I'm not sure what size you are looking for but I know they make them in 1/2". But if you're looking for 3/4" they may be tough to find....

Uponor makes female and street baseboard ells in 3/4 and 5/8