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Community and Q&A

PEX manifold system

cwc09 | Posted in General Questions on

If the goal of PEX manifold systems is to save energy and wasted water on the hot side do you really need a manifold for the cold line? I appreciate the organization and straightforwardness of the manifold system. But if it doesn’t have energy saving potential on the cold side wouldn’t it be more beneficial, in terms of materials costs, to run trunk and branch on the cold side and manifold on the hot? Are there any issues with this?

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  1. GBA Editor
    Martin Holladay | | #1

    You are under no obligation to install a PEX manifold system for your cold-water lines. There are many ways to pipe your home. You can use copper tubing or PEX -- your choice. If you use PEX, you can install the PEX in a trunk-and-branch configuration or a manifold configuration -- your choice.

    You are right that a cold-water manifold does not save energy. I don't think than anyone every claimed that it did.

    If I were using PEX for a new home, I would install a manifold, simply because it simplifies maintenance and reduces the number of fittings in your walls and ceilings. But you don't have to go that route if you don't want to.

  2. Expert Member
    CARL SEVILLE | | #2

    Creating a hot water distribution system that actually saves energy can be very complicated. It is very much dependent on the building design including the distance between the water heater and the fixtures that use it. Installing a PEX manifold system is not necessarily more energy or water efficient than other types of arrangements. Check out the links on the Alliance for Water Efficiency website on the subject, particularly the articles by Gary Klein - they will help put things into perspective for you:

  3. wjrobinson | | #3

    Uponor has nice multi branch fittings that I use at the location of the bathroom for example. There plastic fittings work well for me and I prefer them for now over the metal for most locations and uses. Think about using Uponors sprinkler system set up also which is piped through the cold water supply.

  4. AndrewInChelseaQC | | #4

    If I recall correctly with a cold water manifold you can home run the pex lines to the fixtures with 3/8" pex which should be a cost and material savings over 1/2" pex.

    You'll have to do a bit of research to confirm this and perhaps others could way in on using 3/8" pex over 1/2".

  5. wjrobinson | | #5

    Andrew, 3/8" PEX is not in common use. 1/2" is the standard. Also if installing large tubs or multi head showers we use 3/4". Not saying this is green though.

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