What I am wanting to do is move my PRV out of my crawl space to where my hot water heater is in a finished closet. There are 3/4" lines feeding my water heater and 3/4" lines plumbed in my houses trunk system. I am eventually going to put a manifold in and I was wondering if I would have any issue Teeing off the water heater line to feed water heater and back feed through plumbing lines for the rest of the house and just cap off current inlet from PRV. That way I can replace the galvanized lines in my house a little at a time to keep from having to do all at once. I didn't know if there may be some issues I couldn't think of that I'd run into during the process.. Pressure issues, water hammering since inlet coming from an elevated source, air trapping etc. etc. etc. Thanks in advance for the input.