PEX layout & planning

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by DavidTu, Dec 31, 2010.

  1. DavidTu

    DavidTu Member

    Messages:
    239
    Location:
    Seattle, WA
    I'm getting ready to do the supply lines for a 22' x 33' 2-story residence w/ basement that has one full bath and one powder room. I will have a 1" supply to the house (PE) and was planning to run 1" PEX line to the water heater (tank), which is in the far corner of the basement. Kitchen is directly above water heater as is the 2nd floor master bath. So, all of these runs would be mainly straight vertical shots so I am thinking a manifold at the water heater with homeruns is the way to go for both hot and cold. The powder room is practically dead-center in the house and the supply run to the water heater would pass it. For the powder room, I am thinking it wise to split-off 1/2" cold water runs to the WC and lav and 1/2" homerun for hot.

    I'm using Uponor Wirsbo pex w/ the propex tool.

    • Any recommendations or corrections on what I've outlined above?
    • Any recommendations on the manifold (e.g. copper or EP, etc.)?
    • I am assuming 1/2" homeruns to each fixture is fine, but wonder if it is sufficient for the bath/shower?
    • Assuming I am doing all 1/2" homeruns should I simply run 3/4" from the supply entry point to the manifold (original plan was to run 1" b/c I was going to run 3/4" branches to each area and not homeruns)?
    • I'm planning to use all plastic fittings as I presume them to be as good as brass, comments?

    Thanks for any and all assistance.
  2. DavidTu

    DavidTu Member

    Messages:
    239
    Location:
    Seattle, WA
    No pex guys? Not enough info? Too much info? Help me help you help me.
  3. Terry

    Terry Administrator Staff Member

    Messages:
    15,110
    Location:
    Bothell, Washington
    1/2" lines are fine for the fixtures. Some can even be 3/8" when using a manifold system.
    If this was not a manifold system, you could use two fixtures on a single 1/2" line. For example, a shower and lav could have been run off of one 1/2" hot supply.
    The plastic uponor fittings will be fine.

    Water pipe sizing

    And yes, if you are passing fixtures, you might as well pick them up on the way.
  4. DavidTu

    DavidTu Member

    Messages:
    239
    Location:
    Seattle, WA
    Thanks Terry!

    One last one... regarding the supply to the water heater and manifold: 1" or 3/4"?
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,126
    Location:
    New England
    WHen using pex, you have the advantage of fewer fittings and smoother interior, but the ID is smaller than copper. You may want a large enough supply to the manifold so that you won't restrict flow elsewhere. A 3/4" pex is only a little larger than 1/2" copper; I'd feed it with 1", which is closer to 3/4" copper. Remember, the area has the r^2 factor, so a little difference makes a big change in swept area and therefore max volume available.
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