A tub or a shower is fine on 1/2"
The 6001 Condos in Bellevue are plumbed with 3/8" Uponor.
Seems like manifolds are geared to 1/2". I've already run 1/2" homerun from 3/4" manifold with six 1/2" ports servicing 1.25 baths, kitchen sink, dishwasher, and clothes washer. Now I am having 2nd thoughts on the tub/ shower. The manifold and WH are directly 2 floors below in the basement. GPM is 7-8 at 60-80 psi. I know pex is smaller than Cu i.d. But at least it's Uponor. Should I upsize to 3/4" with reducer near the valve? My concern is adequate water supply volume. Please gauge the strength of any recommendations.
If you only have one showerhead, federal standards limit it to 2.5gpm max. If you are trying to fill a large tub, 1/2" pex may not be the greatest (but mine seems to work fine). You should be okay unless you are trying to deal with a large system.
Important note - I'm not a pro
Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013
No just a basic system. On general I'd rather overbuild than just squeeze by. In this case it sounds like 1/2" would not be that so I'll leave it be. Thanks guys!
pipe size is incumbent to the flow requirements of the homeowner's fixtures. Generally most showerheads are restricted to smaller gpm, unless the restrictors are removed, but we (my ****. co.) install 3/4" hot and cold water inlet and outlet shower and tub valves with 10 gpm shower heards and multiple shower heads fairly often in large residental homes. If you pipe the larger shower or tub valves with 1/2" Wirsbo/Aquapex/Upinor, the customer will not be able to take advantage of the full flow capable of fixture and outlets.