What type of sealing compound to use for this situation

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by Kimster, Dec 15, 2012.

  1. Kimster

    Kimster New Member

    Messages:
    87
    Location:
    Manitoba
    Hi all! Still working on the bathroom reno. I have copper stub-outs with sweat-on brass 1/2 in female threaded adapters at the end. I have stainless steel 1/2 in male threaded external shower valve adapters (Grohe) that need to get screwed into the brass. Any special kind of pipe dope I should be using for this situation - stainless to brass? The threaded portion of these adapters will eventually be covered by tile. If you need pictures, I will get some for you.

    Thanks!
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,262
    Location:
    New England
    You do not need anything special to seal that connection - tape and/or pipe dope will work.
  3. Kimster

    Kimster New Member

    Messages:
    87
    Location:
    Manitoba
    Thanks, jadnashua! I thought I read somewhere that when you're dealing with stainless on another metal, that the pipe dope had to be anti-galling. Maybe this is true of all pipe-dope? Any brand you particularly like? All the stuff in the box stores here is Oatey, but I can go to the plumbing supply for other stuff if there's better out there.
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,262
    Location:
    New England
    Stainless on stainless can cause problems...wouldn't expect you'd have problems with this...plus, it's not like you will be installing and removing it regularly!
  5. Kimster

    Kimster New Member

    Messages:
    87
    Location:
    Manitoba
    Gotcha! Thank you!
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,032
    Location:
    Cave Creek, Arizona
    If this is for a surface "shower wall". are you sure they are not chrome plated brass?
  7. cwhyu2

    cwhyu2 Consultant

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    Location:
    Cincinnati OH
    I am thinking the same way.
  8. Kimster

    Kimster New Member

    Messages:
    87
    Location:
    Manitoba
    HJ and cwhyu2, you're right. I had a closer look at the threads because I had done a test to see how far they'll screw in to a "test" female adapter and I can now see some gold color beneath the silver. Thanks for that. This is the set up I'm looking at and so I'm thinking that any pipe dope is fine for this application? I'm just wondering if you have a preference as to brand of pipe dope. Or maybe you would recommend both teflon tape and dope. The female adapter will be buried in the wall so that the escutcheon plate meets the wall. Would have been nice to have some of that sticking out in case I needed to grab it with pliers at some point, but I'll fasten it down really well so it doesn't move in case I have to tighten or replace something later. I would like to do this so it's permanent and I don't have to ever touch it again. Should this contraption be able to screw in all the way into the female adapter? When I tried the test one, it would only go in so far so that there were about three threads left. That was an older, used adapter and the one I have here is new and I know it will go in farther, but how much should I crank it?

    And yes, this is for a surface shower. The valve gets screwed into the large end of the plated adapter and the escutcheon plate covers that part as it sticks out of the wall. The shower pipe runs surface from the top of the valve body and a handheld runs off the bottom of the valve.

    Thanks!

    grohePart.jpg
    Last edited: Dec 17, 2012
  9. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,262
    Location:
    New England
    I have a similar Grohe. It's a little tricky as the offset is there so that you can get the height AND separation just right for the valve to fit perfectly level. You may find that tape and pipe dope is your friend here, as you can't always just run it around another turn to get it tight AND at the exact position you want it. Also, the depth of that connection must be within range for the valve to be able to tighten down. You really want a drop-ear el in the wall. The way that anchors is by tightening the trim up against the wall, clamping the valve in place only by friction and pulling on the piping in the wall. If the pipe in the wall is not VERY well anchored, it will move and mess things up. You'll be putting the fitting in tension when you tighten the trim on the valve - this tension is what clamps the thing in place.
  10. Kimster

    Kimster New Member

    Messages:
    87
    Location:
    Manitoba
    I had thought of a drop-ear el but at the time, I didn't think it was necessary. What I've done is bored out a hole in a 2 x 8 and cut that in half horizontally so the stub out would be sandwiched in between the two pieces which would be screwed to the studs. The stub-out would be fastened down to the bottom half with a copper strap. I also have 1/2 inch plywood in behind the stub-out so it can also be fastened there with straps and screws and finally, the pex will also be fastened to the plywood with clips. I'm making it so it doesn't twist or pull forward or back. I've measured and made allowances for the 1/2 in Durock, Kerdi membrane and thinset behind, 3/8 tile and 1/4 inch of mud behind it. If I'm right, the escutcheon should cover the part of the adapter that goes into the valve and the rest of it gets buried in the wall. I was also going to crank on the valve adapter before putting the Durock up, leaving an extra bit of space to maneuver the board over it. That way it'll be tightened on before I strap it all in. Let me know if I'm off somewhere or if there's some magical way of doing this without all the math and swearing, lol!

    valve.jpg
    Last edited: Dec 17, 2012
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