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Thread: Planning PEX Pipe/Manifold

  1. #1
    DIY Junior Member eferrini's Avatar
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    Default Planning PEX Pipe/Manifold

    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. Looking forward to getting started.

    Tony

  2. #2
    General Engineering Contractor ballvalve's Avatar
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    Since the water heater is 3/4, may as well stay with it. Run the 1" pex into a 1" copper cold manifold. Plenty of 1" manifolds by Sioux cheap.

  3. #3
    DIY Junior Member eferrini's Avatar
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    Thanks for the input, ballvalve.

    Do you see any issue splitting the main water line just before the manifold to supply the water heater? It seems like most PEX home run diagrams show the main line running to the cold manifold, then exit the manifold to supply the water heater. Any issue with my plan to split before the manifold to supply the water heater like this?

    Also, any noticeable difference between a 1" or 3/4" inch in terms of sizing the main supply or manifold? (I already have a 3/4" supply manifold)

    Thanks again!

  4. #4
    General Engineering Contractor ballvalve's Avatar
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    I would go 1" to the water heater, reduce to 3/4 but feed the cold with 1" -Many manifolds have enough length so that you can cut off the rolled 3/4 crimp [guessing the main manifold is actually 1"] then add a female adapter. But all in all, you could live with the 3/4" in a small house.

  5. #5
    DIY Junior Member eferrini's Avatar
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    I know what you mean about the manifold. Yes, the main manifold tube is 1" and it reduces on the end to 3/4". Maybe I'll try sticking with the 3/4" as it is now, and if I want to improve later we can modify the end of the manifold to 1" as you suggest.

    Good suggestions, thanks!

    Tony

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