Hello all!

Just a quickie. I thought I saw this answer before somewhere, but now I can't seem to find it again.

My question is one of fluid dynamics:

I have a 1/2" (copper) supply coming into my bathroom that changed from 3/4", inside the wall about 4". Impossible to reach without destroying adjacent bath. It was feeding just a shower in this room, but now I want to feed a shower and bath so I need it to be 3/4" for another 15 ft or so....

Can a 3/4 supply line have about a 1 foot section of 1/2" pipe in it without any noticeable drop in pressure or volume?

Plumber buddy says "No sweat". Just put reducer coupling at accessible point and go back to 3/4" for remaining run....."Absolutely NO drop in performance"

Of course I'm here for a second, third, and fourth opinion because this will be feeding a multiple head shower and I'd hate to regret it later.....

Thanks a lot for your time!