Pex manifold design

[Johnjohn]

Im rebuilding a 1922 tampa bungalow, the previous owner attempted to add Pex plumbing and while it works it is just wrong. Missized lengths, not secured wavy running along the ground random capped off sections and weird traps.

So I'm looking to install a home run system with my tankless gas exterior water heater

Possibly 12-14 outlets on each side hot and cold, planning for now and leaving space for additions if someone in the future decides to do anything

What material should I use for the manifold its self along with the fittings? I tig weld and feel more than confident enough to do stainless steel or aluminum, I live in Florida so hard water from the limestone is a concern but I can also add in a way to clean the manifold

Secondly what dimensions should I use 3/4 mains with 1/2 outlets? I've seen too many answers to that question to feel confident with any of them. It's a simple pier and beam house single story so nothing uphill or really far 1 and 1/2 bath

I'm typing this on my girlfriends iPad so I will come back and make this a better more descriptive and complete post hopefully with a layout of the house when I have tome time later

Thanks for the help and input, This will be my first Pex project and I'm in the research phase now any help or leads to resources are much appreciated

 

[frodo]

can you sil floss brazing rod ?

24'' peice of 1'' copper, drill holes insert 3/4 short pcs and sil floss it ?

 

[Matt30]

There are pre fabricated manifolds done in 1" copper with a 1/2" copper x pex ball valve on the branch. I use them all the time for heating.

How far of runs are you going to have? One thing to consider is this. If someone was to want to shave or something in the bathroom basin, then get in the shower, you still have to run water from the basement to the tub before you get hot water. If you were on a traditional branch system, water would already be there because you had hot water from the basin. So depending on the distance water has to travel, you can end up with a lot of wasted water.