1/2 to 3/4 transition

[Drewsonian]

I am moving around well tank / softener / water heater and moving several pipes in the process. I plan to switch from a trunk/branch to a PEX manifold. I have one set of 3/4" hot/cold pipes going to my second floor that feed my two upstairs bathrooms (which I am not changing the runs to the second floor fixtures to home runs at this time) . My question is... most manifolds that I'm looking at have 1/2" outlets. Is it stupid (not ideal, ill advised, against code, etc) to go from 1/2" outlet to the larger 3/4" trunk to the second floor? Otherwise, I would just plan to tee off from just before the 3/4" inlets on the manifold.

Thanks!

 

[Reach4]

If this is a philosophical question, don't describe what you are looking for.

The reason so many manifolds have 3/4 in and 1/2 out is that the 1/2 inch are going to individual fixtures or groups of fixtures (such as the hot for one bathroom).