Planning PEX Pipe/Manifold

eferriniDecember 27, 2011

Hi all,

I'm looking for some advise on planning my PEX project. I am planning to use a home-run system with copper manifolds (1/2", 12 cold, 6 hot)).

I figure that I'll buy the copper manifolds with the 3/4" inlet. However, the main water line to my house was replaced last year with 1" PEX coming into the house. From there everything is galvanized that I'll be replacing with PEX.

Is it okay to continue the 1" PEX pipe all the way to the hot water heater, then split the 1" into a 3/4" to the water heater and 3/4" to the cold PEX manifold, then run the hot water heater 3/4" over to the hot PEX manifold? (so basically, is it a bad idea to split the supply line before it gets to the manifold, even if it's a 1" line?)

We are in a 1,000 sqft house with 2 bathrooms. Is it overkill for me to run 1" pipe at all? Would a 3/4" main line that then splits to the hot water heater and cold manifold work out just fine?

Thanks for your advice as I start my PEX project. I am looking forward to getting started.


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Yes, you can run 1" to the water heater and make the split as you describe, however, before you do anything towards desiging your PEX system I would strongly advise you to download a free copy of the PPFS (Plastic Pipe & Fitting Assoc) PEX Installation Manual.

The manual is a free download in PDF format and it will not only answer your immediate question, it will give you all the tables and design parameters to correctly design your system.

    Bookmark   December 27, 2011 at 3:31PM
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Thanks for the suggested reading. I found a good basic installation guide from Zurn. I'll take a look at this one, too.

    Bookmark   December 27, 2011 at 3:58PM
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