using unions in shower valve plumbing, yes or no?

Discussion in 'Shower & Bathtub Forum & Blog' started by macleod, Jan 22, 2005.

  1. macleod

    macleod New Member

    Jan 22, 2005
    pasadena, ca

    I am redoing a small bathroom, and I've finished the demolition down to the studs and joists. I'm getting ready to rough in the new supply lines to the toliet and sink, but I have questions about plumbing the shower. The new shower valve I got is pressure-balancing and temperature balancing - it's heat sensitive and the inlets are 1/2" female npt.

    Although there's an access panel, I'd rather not use any unions in plumbing this in and sweat as many connections as I can. If I can avoid taking it apart I'd rather, but if it comes to it I guess I would to avoid heat damage.

    Can anyone comment on using unions in general? They seem easier for a diy installation - which this is - but they just seem like they're more prone to possible leaks. Right now I'm consigned to measure everything out and dry-fit everything, then sweat joints as far from the valves before either tightening the threaded connections or disassembling valves and sweating those.

    Would anyone advice sweating a threaded connection? I would prefer not to because it seems that would make disassembly a real bear, but I'm curious.


    Jason MacLeod
  2. Clayton

    Clayton Plumber

    Sep 26, 2004

    No need to install unions. You can cut your lengths of copper and solder them up with your male adapters before installing them on the valve. Depending if there are any studs in the way or not you can even solder the 90* elbows and the lengths of copper for your risers and then assemble them to the valve before installating the valve. Then just make your final solder joints far away from the valve.

    If you already have your supply risers in place and just need to connect to the valve, use as long of piece of copper as you can to solder your male adapters on to. Then install them into the valve, get some Heat Sink, or wrap with wet rags and make your final solder connection there at the 90* elbows. You dont want to burn out all your pipe joint compound. Do the same for the shower riser, solder up the male adapters to the copper and then thread it onto your shower valve and volume control or diverter.

    Good Luck.
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  4. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    If the connections on your body are sweat-only, then by all means dissassemble the valve completely. Do not be alarmed by this procedure; the valve is MEANT to come apart, for repair, etc. Use the diagrams in the user manual. I sometimes take some Polaroid or digital snaps. Take the valve apart in an area which will not be disturbed; lay the parts out on a clean towel, lining them up in the order that you took them out. Reassemble ensuring that no debris or lint has attached to the seals. Any rubber piece that looks like it had some lube on it, a little extra faucet-grade silicone grease is OK.
  5. DIY-joe

    DIY-joe New Member

    Feb 21, 2005
    Boston (metro-north)
    Thanks for the advice on working with threaded fittings

    I bought a Pegasus tub and shower mixing valve and was/am figuring how I was going to install it. I cut the old value out and did a bit of experimenting on it with my torch and solder before I trashed it for good. I was unable to remove the threaded fittings. They appeared to have been soldered after they were assembled.

    I've seen similar fitting that were teflon taped and seemed to work fine so that is how I intend to assemble this.

    I did have a question...can anyone tell me if there is a standard height for this type of control. I'd imagine that there isn't only because I've seen so much variation in the placement of the controls

    Last edited: Feb 22, 2005
  6. OfficeLinebacker

    OfficeLinebacker New Member

    Nov 25, 2006
    I'm about to face this exact issue. I am glad this was discussed. Thumbs up!
  7. Shedtav

    Shedtav New Member

    Oct 25, 2008
    Terrific advice. I am a DIY kinda person, but I have found that there are always little tricks/shortcuts to safely and correctly do the things that really matter. I will take some pix too, excellent idea especially in this digital world..
  8. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    The height of the valve will vary depending on whether you are a "little person" or a basketball player. Put it where it feels good to you, normally between 42" and 48". We do not use female threaded valves because they are normally for the DIY trade. but solder the tubing into the adapter and then screw it in. When a customer furnishes a FIP valve, I usually solder the adapter in so I do not have to worry about defective threads or any other cause of a leak.
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