PEX or copper between valve and tub spout

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by mpears, Oct 26, 2007.

  1. mpears

    mpears New Member

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    Oct 26, 2007
    i have heard that using pex pipe between the tub/shower valve and the tub spout may be a bad idea, as it may cause water to go out the shower when unwanted. not sure why, unless the elbows for pex being on the inside cause a restriction.

    also do newer valves account for this in any way ?

    trying to avoid soldering (i.e. using copper).

    planning to use pex from the valve to the shower head.

    Also have heard that the distance from valve to tub spout s/b between 11" and 18". is this just about esthetics or are there technical reasons ?

    thanks.

    mike

    [​IMG]
     
    Last edited by a moderator: Jul 21, 2017
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    1/2" copper verses 1/2" PEX have the same external dimensions, but the internal dimensions are different PEX pipe walls are thicker, thus smaller and lower flow capacity. Any restriction to the tub spout will often be enough restriction to cause it to slowly backup in the showerhead riser, and dribble out there as well. Plus, there isn't a good way to attach any of the tub spouts to PEX. They typically are either a slip on or a screw on connection. You can't anchor the PEX, so your spout would move and the connection would be a problem. PEX to supply the shower valve is okay but not for the tub spout.
     
    Last edited by a moderator: Jul 21, 2017
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  4. hj

    hj Moderator & Master Plumber Staff Member

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    PEX

    If the distance is greater than that it could also induce enough back pressure to force water out of the shower head. Shorter than that has no problems.
     
    Last edited by a moderator: Jul 21, 2017
  5. mpears

    mpears New Member

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    Oct 26, 2007
    thanks for all the responses; much appreciated. i will look into those drop ears - i'm a bit leary now of the PEX, after running into a guy at the home depot who had the shower rise issue, and the Delta help desk told him to go back to copper. tried to get some info from Moen, but couldn't get thru. i will look into those drop ears.
     
    Last edited by a moderator: Jul 21, 2017
  6. hj

    hj Moderator & Master Plumber Staff Member

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    Pex

    The problem with PEX is the pipe between the valve and spout, NOT the fittings or loose ell. A drop ear elbow is need regardless of the material, but it will not eliminate the back flow problem if you use PEX. Maybe the customers of the pros who "use it frequently" only use the tub as a shower so they do not have the problem.
     
    Last edited: Oct 27, 2007
  7. mammoth

    mammoth New Member

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    I’m glad I caught this. Shower pressure is a big thing for me. That’s why I’m running three-quarter inch pex up from the basement to this new second-floor bathroom. I have no problem sweating copper joints, so this is definitely the way to go for me. I have a feeling that the tub spout will be stronger with real copper pipe instead of the pex stub out I was initially thinking about. Especially because my tub spout is a slip on connector. So pex up to the valves (3/4 inch almost all the way until the last few inches) and copper from the valve to shower and tub spout seems to be a pretty clear solution for water pressure. Unless I decide to just go for 3/4 -inch copper for the valves, too. I kind of wonder if the 6 inches of half-inch pex will restrict flow even a bit.
     
  8. Terry

    Terry Administrator Staff Member

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    You can't use PEX for a tub stub out either. A slip spout needs copper.
    PEX fittings also restrict quite a bit and do push water upward to the shower head.

    [​IMG]
     
    Last edited: Jul 21, 2017
  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    1/2" pex with one shower head would work from a supply situation without reducing your effective pressure, but if you used that as supplies to a tub, you might notice it takes longer to fill it...but, as has been said, using pex to run to a tub spout is bad news. I disagree with the OP's install diagram that says galvanized is acceptable...IMHO, while it can work, it WILL eventually rust...use a brass nipple if it is threaded or a copper stub with a fitting soldered on. Using pex to a tub spout would also mean there's no good way to stabilize it...pex is just too flexible.
     
  10. Terry

    Terry Administrator Staff Member

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    And here are the Delta instructions.

    [​IMG]
     
  11. BruceL

    BruceL New Member

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    Speaking as a DIYer, if the shower valve has threaded connections (I assume it does or pure pex wouldn't have been an option) I wouldn't be too nervous about this being your first experience sweating copper. Practice a bit, then solder the threaded end onto the copper, attach it, and solder the elbow or drop ear onto the other end depending on your situation. Just keep the valve above what you're soldering so you don't drip solder into it. Worst case is you totally mess it up and have to unscrew the copper from the valve, throw it away, and try again.

    Even if it has the combination threaded/solder connections, if you haven't done soldering before I would use the threads. Soldering 1/2" copper fittings is really easy. Brass valving is a bit harder---I've done quite a bit of soldering and the one joint failure I had in my current project was a tub valve.

    Bruce
     
  12. Reach4

    Reach4 Well-Known Member

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    There exists a 3/4" PEX x 1/2" Female Threaded Drop Ear Elbow. This would seem to overcome the absolute injunction injunction using PEX on the way to the spout.

    http://www.pexuniverse.com/3-4-pex-x-1-2-drop-ear-elbow

    This is not for expansion fittings, but rather for compression or clamp.
     
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