I'm no PEX expert but I've got al the tools & have read a great deal
about the stuff.
I'm real old school, always have used copper tube for new & repair
work. I'm just about to take on a re-pipe (80 year old galv) & PEX
will be my choice.
I've been thinking about the two methods & I think I've settled on the
manifold / home run system. At first I thought it was rather wasteful
but I think it's the correct way to go.
yeah the manifolds are a little pricey but all your starting
connections are made in the same place & you just run tube to fixture.
All your runs will have no hidden / unservicable joints. You'll save
money on fixture located shutoffs.
If your're handy with a torch you could build your own manifolds with
here is a source for manifolds with built-in valves
no you're not missing something, you CAN do it with 3/4" straight line
but I think you'll be gving up some of the advantages of PEX.
system performance will depend on usage & home layout. I have a mdeium
sized ranch house that I almost re-piped w/ PEX. I was going with
two sets of manifolds
near the laundry & kitchen
near the remote bath cluster
I was even thinking about a hot water loop to the remote manifold;
water temp & timer controlled. I was tired of waitng 135 secs for hot
btw I already re-piped the street to house main (1" copper two years
ago) & all yard water in 1"PVC. I've got awesome flow anywhere in the
yard. No more house mounted hose bibs.
The house flow is a joke, takes about 15 minutes to fill the washer
and forget about running two fixtures.
I've yet to take the plunge and actually do a PEX re-pipe, so
everything I've mentioned has only be my thoughts on the subject.