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Union surface just metal to metal?

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sunlight33
sunlight33 Member Posts: 378
in THE MAIN WALL
The contact surfaces on the Viega union fitting is just metal to metal, I presume this is going to be watertight after tightening but no gasket is needed?

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  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,524
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    Yes, metal to metal, no gasket needed. The Viega unions are usually very good high quality and don't leak. They shouldn't for the price they get.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,837
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    A modern marvel of precision engineering! And they had metal to metal unions even before NASA was around! Check out that radiator valve
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • Jamie Hall
    Jamie Hall Member Posts: 23,286
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    Just remember that a union will not correct for misalignment, either laterally or vertically or angularly. And don't be a gorilla when you pull it together!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    PC7060MaxMercy
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,837
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    @Jamie Hall... I have used Gorilla in the past for many things. Some even use it for hair care.
    Have you tried their Bikini Wax product?
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • Jamie Hall
    Jamie Hall Member Posts: 23,286
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    As they used to say about duct tape... it's like the Force. It has a dark side and a light side, and holds the universe together...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 22,143
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    metal to metal unions usually have some taper or bevel, not a flat surface. If it is flat to flat, I think a gasket would be needed?
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Rich_49
  • JUGHNE
    JUGHNE Member Posts: 11,061
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    Always had good luck with brass/brass unions.
    Stainless steel on the other hand can be tricky.
    Steel is hard unlike brass that might conform just a little to the match up.

    Gas and water meter spud unions use a flat washer gasket.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,524
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    @JUGHNE

    Copper sweat unions are problematic. The cheap copper-copper ones if you put 10 of them in correctly a few will drip. The you dope them and hope for the best.........does not make me happy. I usually don't dope any unions unless I have to but like using never seize.

    On copper I have much better luck with the Nibco where 1 end is copper and the other end is brass, forgot the # Those are pretty good.

    Of course, because the are more $$$$ some supply houses don't stock them. Big Box forget about it.

    The propress unions are big $$$$. I don't think I have ever had a leak on one of those. Quality counts
  • JUGHNE
    JUGHNE Member Posts: 11,061
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    Those NIBCO brands have been pretty good.
    I have salvaged some old (30-40 years old) that performed well.
    I did learn to not assemble the unions before soldering....a little solder in the wrong place will ruin your day.
  • pecmsg
    pecmsg Member Posts: 4,847
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    JUGHNE said:

    Those NIBCO brands have been pretty good.
    I have salvaged some old (30-40 years old) that performed well.
    I did learn to not assemble the unions before soldering....a little solder in the wrong place will ruin your day.

    Again a little never seize goes a long way in preventing that!
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,524
    edited April 2021
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    @JUGHNE

    Tell you the truth in my younger days I soldered many together :) NIBCO makes the good ones and the cheap ones @pecmsg that sounds like a good trick with the never seize.

    I always solder them when apart just to avoid that problem.

    Finally learned to much (or how little) solder to use
  • mattmia2
    mattmia2 Member Posts: 9,646
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    I had to wipe the solder off of the taper of one...

    I had a 1" black iron union from home depot that i had to replace with one from the real hardware store because it was leaking. A lot of times the iron ones have a brass seat in them.
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,524
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    @mattmia2

    You only had to wipe the solder off one?? Your better than me!! :)
  • mattmia2
    mattmia2 Member Posts: 9,646
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    I have only used a couple dozen...
  • sunlight33
    sunlight33 Member Posts: 378
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    I used two Viega unions today on a water filter housing, unfortunately both would weep afterwards, I tried reposition the pipe, added pipe dope to the thread and used more torque to tighten it, none mattered. The leak wasn't bad, just a drip or two every minute or so but I don't feel safe about it, didn't expect $30 a piece to perform like this. =(
  • mattmia2
    mattmia2 Member Posts: 9,646
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    I have sealed up especially copper unions by putting a couple wraps of teflon tape on the bevel although some will disagree with this method.
    PC7060
  • mattmia2
    mattmia2 Member Posts: 9,646
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    I think it is possible to distort and crush them with a prench that clamps down as you turn like a pipe wrench. i have also gotten them to seal with 2 very large wrenches. Remember the union nut is a couple sizes larger than the pipes it is mating together.
  • sunlight33
    sunlight33 Member Posts: 378
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    The other press union sold on supplyhouse (JW) has a rubber gasket, maybe this type is less prone to leak than the ground joint type?
  • mattmia2
    mattmia2 Member Posts: 9,646
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    initially. until you take it apart at 6 pm on a saturday 20 years later and the gasket is rotted out and you have to figure out something else to seal it up with.
    PC7060
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,524
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    @sunlight33

    Surprised you had trouble with the Viega unions they are usually pretty good. Try some teflon tape and never seize
  • sunlight33
    sunlight33 Member Posts: 378
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    Good news, I loosened the bracket holding the water filter housing and realigned the pipe to make sure it's square to the union, now the leak has stopped.
    But the bad news is that the water filter housing starts to leak after I tighten it with a new O-ring.
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,293
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    Maybe use a copper flex line between them? :p

    Yours, Larry
    PC7060
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 15,524
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    @sunlight33

    Sounds like things are not lined up
  • sunlight33
    sunlight33 Member Posts: 378
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    Yep, I learned something new today, tightening the nut on the union will not help align the pipe if they are not lined up to start with.
  • sunlight33
    sunlight33 Member Posts: 378
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    Right now I am running pressure test with the filters before I put it into use. All joints and the filter itself are dry, but the pressure gauge is showing a pressure drop (1 psi every 1-2 hours), is this normal to be leak free?
  • mattmia2
    mattmia2 Member Posts: 9,646
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    It is leaking somewhere but i'm not sure i would expect those o-rings on the housings to be airtight if you are testing with air.
  • sunlight33
    sunlight33 Member Posts: 378
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    mattmia2 said:

    It is leaking somewhere but i'm not sure i would expect those o-rings on the housings to be airtight if you are testing with air.

    I am testing with water. So perhaps this is fine and I can move on to the next filter, got three more in the system, lol.
  • mattmia2
    mattmia2 Member Posts: 9,646
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    could be temp changes. if it is leaking where the water is you would see it
  • Jamie Hall
    Jamie Hall Member Posts: 23,286
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    If you're testing with water, and there is little or no air in the system, the pressure will be ridiculously sensitive to temperature. A good check, though, is to see if it stabilises when the temperature does, or better yet see if it goes back up in things get warmer.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • sunlight33
    sunlight33 Member Posts: 378
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    No sign of going back up, still losing about 1 psi every 2 hours, someone suggested that the pressure relief button on the housing could be the culprit.
    Another thing I learned is that if the system has no leak then the pressure gauge will start to rise as soon as I open the valve to let water in, because the water is compressing the air inside, it's a quick way to detect leak.
  • mattmia2
    mattmia2 Member Posts: 9,646
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    are you pressurizing it from the municipal system and leaving it connected? try bringing it up to like half the municipal supply pressure and see if it slowly rises because the valve isn't holding.
  • sunlight33
    sunlight33 Member Posts: 378
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    It has valves on both the inlet and outlet, so once it's pressurized from the city water I turned off both valves, the valves themselves should be leak free.
  • mattmia2
    mattmia2 Member Posts: 9,646
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    should
  • mattmia2
    mattmia2 Member Posts: 9,646
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    Look closely around the packing on the valves as well, although if it is a ball valve that should be sealed off when it is closed, I have bought a lot of ball valves with loose stem packing nuts. If they are sweat type valves the heat can cause the plastic to flow and become loose as well.

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