I'm redoing the water lines in my old home.
I'll be using Dura-Pex pipe. I plan to use 1/2" pipe to all the fixtures. Wasn't sure whether to use 3/4" or 1" for the main lines into the manifolds. Will either help increase water pressure to the fixtures?
Yes, the main line feeding the manifold should be increased for volume and not pressure. You should only have one manifold which all lines come off of. You purchase your manifold with the number of connections needed. Volume is the major concern to feed the manifold for a number of fixtures units operating at the same time.