How to connect a female threaded shower valve

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by mike__b, Jul 9, 2011.

  1. mike__b

    mike__b New Member

    Messages:
    6
    Location:
    KY
    I've never installed a shower valve, and the instructions are laughable. However, it is a new Moen with female threads for each supply and output. As opposed to brass fittings with male threads, you cannot directly solder to the valve as an alternative. As a secondary question, I read to both do and don't use teflon on the threads. I always have in the past, even with some compression fittings, and I would normally use teflon for these connections.

    So I figured I have a few options. I'm running PEX as my supply, but I planned on sweating copper to the shower head for rigidity.

    1) Sweat male threads onto copper stubs, let cool, install into the shower valve body before installing into wall. I just need to lay everything out ahead of time near the valve.

    2) go all PEX and get male threaded PEX adapters. Insert the PEX fitting into the valve, install valve, then come back and install the supply lines.

    If someone could suggest an alternate method as well, I would appreciate it.

    As a side note, the only way I've seen this installed in an all copper setup is to install male-male fittings in each valve supply, then sweat on male thread fittings on the copper supply lines. The connection is then made by a flexible, rubber supply line like for a faucet. Otherwise, I'm confused how a remodel or other all copper install would even work due to the teflon issue.
    Last edited: Jul 9, 2011
  2. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,358
    Location:
    Yakima WA
    Solder a nipple to a threaded male adapter. Screw the male adapter into the valve, shorten the nipple to the length and go from there. You could cut the nipples to length before soldering to the adapter if you wish, but sometimes it's easier to determine the length with the piece in place. Either way, you do not solder anything to the valve body.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,129
    Location:
    New England
    Some of the plumbing parts are made poorly, and the threads are rough. In those cases, it may work better to use both tape and pipe dope. You can solder a nipple into the valve, but if you ever needed to get it out, it would be very difficult. Ensure you take the cartridge out first if you decide to go that way.
  4. Terry

    Terry Administrator Staff Member

    Messages:
    15,118
    Location:
    Bothell, Washington
    Moen makes their valves three ways.

    CC, for solder connections
    IPS, for threaded
    PEX,

    Normally plumbers will buy the CC sweat valves. The home centers always sell the IPS valves. Just one more reason to not buy there.

    If you connect with copper, solder a male adapter onto copper, let it cool and then either Teflon, Teflon and pipe dope or pipe dope it.
    Yes, there are three correct ways to do it.

    The valve has to be secured to something solid.

    The shower head can be run in PEX. If you have a tub spout, that has to be full size pipe. Copper or brass nipple.
  5. mike__b

    mike__b New Member

    Messages:
    6
    Location:
    KY
    You can't solder anything into the valve assembly, they are female threads.


    Thanks. I'll probably just run it in PEX with the brass male thread fittings into the valve and a pex drop elbow for the shower as well.
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,129
    Location:
    New England
    Yes, you can solder a threaded nipple into the threaded valve, but you would likely never get it out again and you might get some solder into places it shouldn't go, but it is possible and would make a solid, leak-free connection.
  7. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,811
    Location:
    Cave Creek, Arizona
    quote; The connection is then made by a flexible, rubber supply line like for a faucet.

    No self respecting plumber would EVER install ANY valve that way. It is strictly a handyman/homeowner method, and those supply lines are labeled "for EXPOSED locations only". If you are using PEX, the screw male adapters into the valve. You have to use SOME KIND of sealant on the threads.
    Last edited: Jul 10, 2011
  8. mike__b

    mike__b New Member

    Messages:
    6
    Location:
    KY
    I agree. I ended up using threaded 1/2" PEX adapters, then just running the pex to the valve. No soldering involved. I used teflon tape just because I've never used pipe dope on pressurized lines before.
  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,129
    Location:
    New England
    Either pipe dope or teflon tape will work. That assumes they are installed properly and the threads and fittings are up to spec. Some of the junk supplied today (often from China) does not meet specs, as the threads are rough (the tools are dull), the threads are not the proper length, or the sizing is slightly off. Then, the belt and suspenders of using both can fill those spaces and prevent leaks.
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