I've finally started my bathroom remodel and have mostly completed the demolition phase. I've removed everything down to the studs, including removing the existing glav steel. I'm planning on using PEX as the replacement in the Master bathroom, following it up with replacing all of the galv steel pipe I can reach in the rest of the attic.

My question is, and I apologize if it's been asked before, is since the ID of PEX is smaller than the Galvanized pipe, I was thinking of running 3/4 inch PEX to the shower valve with a 3/4" PEX to 1/2" NPT fitting for the connection. The ID of the 1/2" PEX seems so small, I'm concerned with low flow at the shower. Any thoughts? Does this sound reasonable? The shower will consist of a hand spray, three body sprays, and a overhead rainshower.

The overall plan is to run a hot and cold 3/4" trunk line and drop off to 1/2" for each of the vanities and toilet, with a 3/4" drop for the shower. I also have considered a small manifold, one each for the hot and cold, which I may do if the feeling is that 1/2" feed to the shower is appropriate.

Any feedback is greatly appreciated.