Solder threaded copper?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by jhighley, Feb 16, 2007.

  1. jhighley

    jhighley New Member

    Messages:
    4
    Can a threaded copper joint be soldered instead of using teflon tape/creams/etc. ?

    I have Moen tub/shower valve that suddenly seemed to get plugged on the hot water side. I remove the valve core and didn't see any issues. With the core removed, I turned on the hot water and nothing flowed into the valve. I tried pushing some wire from inside the valve out into the water line, but no luck. I can't imagine what would suddenly plug the inlet, but that's the only cause of the problem I can come up with....

    I guess I'm going to un-solder the water line next to the valve and see if something is actually plugging it at the valve inlet. The valve is threaded female. The threaded male copper is soldered directly to a street elbow. I plan to unsolder at the street elbow - male adapter connection. My concern is that the heat from soldering the joint will burn the teflon tape in the threaded joint and it will leak.

    Instead of using tape or cream in the threaded joint, can I solder it?

    Thanks,

    Josh
    Last edited: Feb 16, 2007
  2. jhighley

    jhighley New Member

    Messages:
    4
    Sorry, that was kinda long. Too sum up my question:

    Can I solder the threaded joint on a tub/shower faucet instead of using teflon tape or pipe dope?

    Thanks,

    Josh
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Soldering threaded connections is not really the right thing to do. It would be hard to get everything clean enough, and the solder may not flow adequately. I belive it has been done, though.

    Did you ever burn the teflon on a frying pan? No. Tape and dope will withstand the temp of soldering.
  4. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,332
    Location:
    Yakima WA
    I would not. There's a reason plumbers don't solder those joints. You would have to apply too much heat to the valve body and you'd risk damage to it. Some guy like tape, some use pipe dope, and some both at the same time. So go figure. My weapon of choice is pipe dope because (a) it's so easy to use especially in tight spaces and (b) it does the job. The only down side IMHO is it can be a tad messy, but you're usually not in an area where that will really matter and it isn't really difficult to clean up if necessary.
  5. jhighley

    jhighley New Member

    Messages:
    4
    The problem is that I have to install the male thread adapter into the valve body, and then solder a street elbow to the adapter. There's not much wiggle room with the pipes. So, I end up heating the valve body a lot, regardless.

    This is the second valve that's been installed. The original had solder connections and my guess is the plumber didn't heat the valve body enough to make a good connection. Early one morning, I awoke to find water streaming from my dining room ceiling, which is below this valve in the 2nd floor bathroom. Both joints for hot and cold water had failed. The repair plumber recommended I get a valve with threaded connections. He had to un-solder one of the joints b/c one of the threaded connections leaked after he installed the new valve. He also discovered there was no pressure regulator on the supply line in the basement, which I'm sure contributed to the joints blowing.

    I guess I'll stick with tape and just tighten it as best I can.

    Thanks,

    Josh
  6. creams?

    I need to go edit a couple postings quick before someone finds them. :p :p :p
  7. Bob NH

    Bob NH In the Trades

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    3,317
    Location:
    New Hampshire
    The way to prevent overheating the valve body is to make the first solder connection to the male adapter before the male adapter is screwed into the valve body. You can usually solder on a short length of tubing, screw it into the valve, and then start the rest of the run. You can usually make up those first joints on the work bench and screw them in before you put the valve in position.

    If the next joint is close, put a wet rag on the valve body to keep it cool while you are soldering the next piece.

    One trick to soldering is to apply heat to the fitting until it is hot enough to melt solder applied to the joint between tube and fitting on the side OPPOSITE where the heat is applied. Then withdraw the heat and quickly apply the solder all around.

    You will have a much higher percentage of good joints if you use a tinning flux such as Oatey No. 95. The solder in the flux immediately tins the joint and prevents oxidation, so the solder flows easily into the joint.

    You always take the guts out of the valve body before you solder to it or close to it. That protects the nonmetallic seals. That is how real plumbers do that job.

    You also want to be sure you don't get globs of solder in the the valve passages.

    Lack of a pressure regulator didn't cause the joint to fail. The joint of a copper pipe properly soldered into a valve body is far stronger than the pipe. The tin/antimony solder that is permitted to be used for water systems is much stronger than the lead/tin that has been prohibited for around 20 years.
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,503
    Location:
    Cave Creek, Arizona
    pipe

    I solder about half of my male adapters into the valve bodies. That way I am sure not to have a leak at the thread.
  9. Racer814

    Racer814 New Member

    Messages:
    124
    nothing wrong with soldering the male adapters into the valve body...done it many, many,many times:p


    that joint probably failed because the valve body threads weren't cleaned properly.....and the heat was applied in the wrong place or not long enough....takes longer for the brass valve body to get hot than the copper male and if your heat is on the copper or the junction of the two then the male will heat up enough for the solder to flow but it will only flow around the end and "cap" the joint versus flowing into it.....
    Last edited: Feb 17, 2007
  10. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,503
    Location:
    Cave Creek, Arizona
    adapter

    Another problem with soldering the joint while the adapter is screwed into the valve is that the adapter is going to expand faster than the valve it is screwed into. That will cause pressure in the thread and when things cool down the adapter could be slightly undersized from the pressure exerted on it, or the valve thread could be slightly oversized, because the two pieces have expanded and contracted at different rates.
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