Pex manifold system/Home run system

Discussion in 'Plumbing Forum' started by emky, Aug 17, 2010.

  1. Aug 17, 2010 #1

    emky

    emky

    emky

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    We are building a home and are having this put in our home...just looking for some feedback from anyone who has any info on it. I opted for this as to prevent the temperature change when running shower, dishwasher, washing machine at same time. And the pex was recommended to us rather than using copper. Any opinions, pos/neg? Thanks : )
     
  2. Aug 18, 2010 #2

    Puddlesx5

    Puddlesx5

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    The only issue with the manifold system is, if you run the hot water to the

    shower and say lets say it takes 20 seconds to get the fixture hot . It will take

    the same for the sink in the same room. So if water conservation is your thing

    this not the system for you . You will not be able to run a return line very easily

    in this system to heat the pipes to help fix this flaw. But if the runs are short

    go for it.
     
  3. Aug 18, 2010 #3

    gatorfan

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    Or, if you don't often use hot water at the bathroom sink (or family almost never does), you'll save a lot of hot water and get it quicker using a home-run/manifold system. BTW, PEX doesn't have to be home-run-- you can run trunk-and-branch if you want (but hot water time will be similar to copper).

    Matt
     
  4. Aug 18, 2010 #4

    gatorfan

    gatorfan

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    Forgot to mention, home-run won't solve the problem you mention. That can only be solved with a bigger hot water heater or point-of-use/tankless heaters.

    Matt
     
  5. Aug 18, 2010 #5

    Puddlesx5

    Puddlesx5

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    The problem I mention is not a heater issue it is a pipe length issue. Shorter pipe shorter wait time for hot water,longer pipe longer wait. A water heater has nothing to do with the question or my response.
     
  6. Aug 18, 2010 #6

    inspectorD

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    The good thing about pex is it is cheaper on labor to install. The best thing about it so far though , is that if it freezes anywhere, it does not break the line. It can still break where it connects to the fixture, but the line maintains its memory.
    We use the new stuff on all new jobs.
     
  7. Aug 18, 2010 #7

    gatorfan

    gatorfan

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    Yikes, no coffee yet? My second comment was made in response to this sentence in the OP's post:

    A properly-sized trunk-and-branch system (as normally used with a copper and some PEX installations) can supply enough hot water volume for all of these uses simultaneously. The issue is normally making enough hot water.

    Matt
     
  8. Oct 31, 2010 #8

    serpentine5

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    I have used and installed pex a few times, and it has held up awesomely. I have done both trunk and branch and homerun systems. if you put the manifold as centrally as you can, or closer to the area it will be used most, you wont have any issue with long extended waits for hot to comeout. It all depends on where the water heater is in correlation to the manifold in correlation to the outlets. If the basement is where the water heater is going, and you put it directly under the kitchen, and put the manifold in the same area, and the master bathroom is 30 feet from the kitchen, you will have hot water almost instantly in the kitchen where you will have a longer wait for the hot to get to the master bath, especially when you dont use the master bath hot but once or twice a day.
     
  9. Oct 31, 2010 #9

    Redwood

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    Have a look see at this guide...
    http://www.toolbase.org/PDF/DesignGuides/pex_designguide.pdf

    When I run Pex I usually use a Trunk and Branch system similar to what is shown in figure 7-1 on page 37.

    In a larger home I will modify that into a Trunk and Branch system with Remote Manifolds similar to what is shown in figure 7-3 on page 38

    As far as wasting water waiting for hot water to arrive that is easily rectified in either if these 2 designs by installing a recirculation loop from either the last fixture on the Trunk and Branch or from the Remote Manifolds on the other. The recirculation pump can be triggered in a variety of ways but my preference is using occupancy sensors.

    Recirculation is not possible on a home run system.
     

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