PEX tubing manifold - use 1/2" or 3/8" inch?

[jamesborn]

I will be replumbing our new old 1930 home with PEX tubing. I have studied some of the installation materials and have decided to use a PEX manifold system. I know it will cost me a few more bucks in pipe and materials but I like the idea of a more professional looking job, as well as the isolation aspect of each run.

One of the manifold installation guides I reviewed suggested using 3/8" lines off the manifold to get the hot water to the fixture sooner. Most of the discussion I have seen on the internet forums shows people suggesting 1/2" runs vs 3/8".

3/8" seems as if it should be a little more flexible and be able to withstand a tighter bend radius, although the way things line up in my basement that really will not be an issue. What am I losing by using 3/8 vs 1/2 lines?

[Redwood]

Why? I have never see a manifold home run system that looked professional....

It always looked like a mess of spagetti to me...

I'd strongly consider Trunk & Branch or, a Modified Trunk & Branch Using Remote Manifold(s)...

http://www.toolbase.org/pdf/designgu...esignguide.pdf

There are many advantages a system like that has over a home run system...

[jamesborn]

one of professional pex manifold system .... look at attachment

[rmw]

3/8 will give you more head loss(friction in the pipe) but will take less time and water to get hot water at a sink or tub after the pipe has cooled due to no use. 1/2 will have less head loss but stores more water in the pipe so you have to run out more water to get it your hot water at the tap. This of course assumes no re-circulation of hot water.

[jamesborn]

thank you for your advice I will prefer 1/2 size

[HayZee518]

half inch sized pex will provide more water [volume] than a three eighths line. 3/8s will provide the pressure but not the volume of water. pex can be snaked through walls like electrical wires. most of the pex is hidden within the walls except where it is connected to a manifold in the basement. for hot water to be available at an instant consider a hot water loop type system. hot water is supplied by a circulator pump connected to your hot water tank and a loop system of pipes or tubing around the house. tap offs can be 3/8" to feed the supplies.

[Redwood]

Ahh the long wait for hot water at every fixture.
It's the Achilles Heel of the home run system...
With a trunk and branch system you can have a recirculation loop from the furthest point(s) on the line or from the remote manifold so hot water is right at every fixture quickly....

I like the picture you show...
It may look pretty right at the manifold but a few short feet away all that prettiness turns into a bundle of spagetti with 20 tubes in it.

Now take those 20 tubes and hide them in a wall and imagine the increased chances of the PEX catching a drywall screw or even a nail when you hang a picture...

BTW that picture is a hydronic heating system and is not a potable water system.

Your profile location says Chicago, I would check your local plumbing code to see if PEX is an approved material in your application.