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Community and Q&A

Pex A Manifolds

Andy Fellenz | Posted in General Questions on

I’m planning the hot and cold water runs for my ranch house gut job renovation.

I will be using Pex A for the water lines and am thinking of doing home run style runs with the manifold(s) adjacent to my well pump and water heater in a utility area of the basement.  I’d like the manifolds to be valved to ensure that I can easily access the valves, rather than having valves in cabinets under sinks, behind access panels and in other difficult to reach locations through out the house.

My mobility is unfortunately limited (I can walk, but have a spinal injury that makes it very difficult for me to bend over and get up and down off the ground) and having everything in one location will ensure that I can set it up at an accessible height and in a well lit and easily accessed area so that I can continue to operate and maintain the system as I get older.

It looks like I will have at least 14 cold water and 14 hot water delivery sites in the house when it is complete

1) 3 cold outside water spigots (can be on a single manifold valve)
2) 1/2 bath in basement with 2 cold and 1 hot (toilet, sink)
3) kitchen with 2 cold and 2 hot (sink, dishwasher, fridge icemaker)
4) guest bath with 3 cold and 2 hot (toilet, sink, tub)
5) master bath with 3 cold and 2 hot (toilet, sink, shower)
6) plant room with 1 hot and 1 cold (potting bench sink)
7) laundry room with 2 hot and 2 cold (washing machine and sink)
8) family room 1 hot and 1 cold (wet bar sink)

Some questions I have are:
1) what are people typically using for manifolds?  Home-grown manifolds? Uponor manifolds?  Another brand?

2) Is there an issue teeing off the cold water side of the bathroom sink to the toilet?  There’s usually just one person in the room and if they’re flushing, they’re unlikely to be using cold water in the sink

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Replies

  1. Aaron Beckworth | | #1

    I like the idea of assembling a custom manifold with high quality valves. There was a really good FHB article on this a few years ago.
    https://www.finehomebuilding.com/2016/07/06/build-pex-manifold

  2. DCContrarian | | #2

    Why Pex A? I find Pex B has a lot more availability for things like manifolds.

    1. Andy Fellenz | | #3

      Why Pex A? I have a Milwaukee expander to do the Pex A fittings and I prefer the close to full diameter flow allowed by Pex A.

    2. Trevor Lambert | | #6

      PEX A is also less likely to leak, in my limited experience. The joint is simpler, and easier to do with the correct tool. You can do tighter bends, and if you accidentally kink the pipe, it can be fixed (PEX B is ruined if you kink it).

  3. Expert Member
    Akos | | #4

    I've tried a number of ways to run plumbing and find the full home run setup to be inefficient.

    Besides ending up with a lot of piping, the wait times for hot water are pretty long especially for something like a bathroom sink. It also makes adding a recirc next to impossible.

    I find a semi-home run setup works much better (at least for hot water).

    The idea is to put each shower on its own home run and everything else on a 1/2" trunk and branch. This way you get full pressure to the showers without any issues with pressure drops from usage elsewhere. Any high usage faucet , such as outdoor spigot or pot filler, should also gets its own home run.

    Means a bit more fittings, but way less piping. It also avoids having stagnant water sit in the lines feeding bathrooms that are rarely used.

    If you really must have a full home run, I would size the piping based on the actual expected flow rate. For example, most sinks and low flow showers can be fed by a 3/8 pex line which has about half the volume of 1/2" pex.

    I always T the toilet off the cold water of the sink.

    1. Andy Fellenz | | #5

      Thanks for the info. and addressing the toilet question. I appreciate your perspective re efficiency, but I am trying to balance that with disability. In this case, disability wins. Forced retirement to SSDI sucks, but life goes on and I'm trying to find work-arounds wherever possible.

    2. Trevor Lambert | | #8

      The hot water wait times won't necessarily be helped by having trunk and branch. Only when another device on the same trunk has been used very recently, which might not be very often. Reducing the pipe size would work every time.

      1. Expert Member
        Akos | | #9

        Trunk and branch won't necessarily get you quicker hot water but will allow for recirc.

        If you have some height, this can be as simple as a thermosyphon loop with a direct acting solenoid valve with a timer for control. My other favorite low tech option is to install a low temperature mixing valve for the toilet. This way every time the toilet is flushed, any cold water in the lines gets flushed as well.

        A bathroom sink in most cases will have about 20' to 40' of line, with a 1GPM tap and 1/2" PEX that is 15s to 30s of wait.

  4. Patrick OSullivan | | #7

    I like the Sioux Chief manifolds that come with Dahl valves. For the amount of labor they save, I think they are a good value. You can buy from PEX Universe online: https://www.pexuniverse.com/pex-a-expansion-copper-manifolds

    1. Andy Fellenz | | #10

      Thanks for the pictures. The installation looks nice. Do you have any experience with MANABLOC systems? I'm wondering how they might compare to the Sioux Chief.

      1. Richard McGrath | | #11

        I would encourage something other than the manabloc product . Have torn many out with several issues . I like the product that Patrick posted . Your specific issues will be addressed by that and no tools are required to turn off valves , just your hand . Hot water delivery time should not be a giant issue as 1/2" pex does not contain that much water per foot , the average faucet would drain the sitting cold water in about a quarter minute . Keep in mind that this is only if a recirc system of some sort is replenishing the hot manifold , keeping the manifold right at the water heater helps greatly without a recirc apparatus .

        You can certainly tee the water closet off the lav or tub/shower cold , the caveat is if someone does flush while your showering you can have temp and pressure fluctuations .

  5. Wooba Goobaa | | #12

    We went with a custom built manifold. Parts can be individually serviced when they fail.

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