Feeling unintelligent... also plumbing question

[BranchingHammer]

Look what I just did! :confounded-face:

Those are two components of unions that can't be used because the screw-on cap can't fit over them now One of those union components is from a true union cepex ball valve, and my question is whether I can replace the grey schedule 80 component of the union with a white schedule 40 one? I'm assuming it's ok, but wanted to check. Here's a picture:

 

[Tenecor Aquariums]

As long as the sizing is correct and that is what you want to do, no problem. 80 and 40 will weld up nicely.