How tight - copper to brass threaded fittings

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by tfratzel, Jan 7, 2005.

  1. tfratzel

    tfratzel New Member

    Messages:
    10
    I recently bought a Kohler shower mixing valve. The valve inputs and outputs are all female treaded. I'm assuming that I can solder a copper threaded adapter to my 1/2" supply lines and then screw that directly into the valve. I'm just curious about two issues before I try this on the expensive valve.

    1. Pipe dope or teflon tape?

    2. Are there any general rules of thumb on how tight to tighten these kind of fittings?

    I'm fairly new to plumbing skills.....finally I'm able to solder and hopefully with some advice I can make these threaded connections without any hidden leaks in the wall.

    Thanks,
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,262
    Location:
    New England
    Kind of hard to screw it into the shower valve after you've soldered the fitting on! You need to screw it into the valve, then solder it. Now, if you have the room, you could use a union too, this would allow you to solder the stuff up without it actually screwed into the valve, then insert it, then tighten down the union. This would give you the ability to loosed the union up, tighten the fitting into the valve if it leaked, then retighten the union without having to unsolder the stuff. Now, this involves more soldering, and is another thing thatcould leak, but you wouldn't risk overheating and ruining your shower valve, either.

    Someone said that some of the threaded valves will also accept a sweated in piece of pipe, thatcould give you another option if it worked.

    Somewhat depends on how much room you have and how skillful you are.

    I'd practice some on some scraps first - cheap insurance.

    The key to a good solder joint is make the pipe and the fitting clean, cover well with flux, move the torch around the joint and get it hot enough to melt the solder without having to have the flame on the solder, then cleaning it off after you get the solder to flow throughout the fitting.

    Note I'm not a pro, but a decent DIY'er...
  3. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,384
    Location:
    Yakima WA
    copper to brass threaded fittings

    To keep for getting the valve usit hot, solder a male adapter to both ends of a short lenght of pipe. Depending on your layout, you might want to elbow one end for easier access. Then screw these assemblies into the valve and secure the entire valve assembly. For easy connections, I use flex tubing to bridge the space from the valve to the supply lines. This does require a couple of extra fittings and soldering, but you don't have to measure and cut perfect lengths, you avoid possible damage to the valve by overheating, and the short pipes give you additional anchoring points to solifify the valve assembly. May not be what a licensed plumber would do, but it works for me.
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,034
    Location:
    Cave Creek, Arizona
    valve

    Throw the adapters away. You can insert the tubing into the valve directly and solder the tubing to it.
  5. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    hj, he has female threads on the valves. What you say works on like Delta, which if threaded it is male threads, and slip fit 1/2" copper.

    As the tightening, hand tight then one full turn wrench. This should be good, but it takes some "feel" to recognize when tight is tight enough.

    Tape or dope is fine. Lot's of people use both together. Whatever trips your trigger.
  6. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,034
    Location:
    Cave Creek, Arizona
    kohler

    Interesting, and I missed that, but I have not seen a Kohler single handle valve with female threads for a long time. All the modern ones have had male/solderconnections. In fact they had them before Delta even thought about doing it.
  7. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    I looked up the ANSI specs on standard taper pipe threads:

    1/2" NPT should engage 4 and one half turns by hand plus three wrench makeup turns for a total lenght of engaged thread = 0.534"

    The standard allows a tolerance of plus or minus one turn. Also it is noted that in practice, threads are often cut shorter than the standard thread length. Due to the taper, this automatically reduces the # of turns for hand tight and wrench. SO we are back to the fact that there is no substitute for the "feel" that comes only with experience, to know when "enough is enough".
  8. tfratzel

    tfratzel New Member

    Messages:
    10
    Thanks for the replies

    This valve (Kohler K-306) only has female threaded inputs. If it had the male ones I'd solder it for sure. From everything I've read it seems to me that the best bet is to pre-solder a short horizontal piece of copper to the male adapter, then thread it to the valve prior to soldering on the elbows. My biggest concern is getting the threads tight without going too far. One person recommended hand tight plus 3/4 to 1 full turn with the wrench.

    Seems like if I have the room I may want to insert the union to give me an easier option of re-tightening the threads if in fact they leak.


    Thanks again everyone....hopefully I'll be succesful!
Similar Threads: tight copper
Forum Title Date
Plumbing Forum, Professional & DIY Advice how tight/loose to hang copper pipe? Jul 8, 2012
Plumbing Forum, Professional & DIY Advice tightening copper fittings Jun 10, 2009
Plumbing Forum, Professional & DIY Advice Need to install a PV Supervent on a tight system Nov 7, 2014
Plumbing Forum, Professional & DIY Advice is it possible to over-tighten tub drain flange? Sep 1, 2014
Plumbing Forum, Professional & DIY Advice Shower head with tightest spray? Jul 23, 2014

Share This Page