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stress on copper pipe

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  • stress on copper pipe

    Sorry if this is a newbie question....
    Is it ok to fasten 1/2 inch copper pipe in a position with a little stress on it? I would like to put a 3/4 inch spacer behind a shower valve so the knob will penetrate the wall a bit more. I can move the valve unit out far enough without too much trouble, but it will be wedged and under some stress in that position. I know I wouldn't want to be stuck in some stress position for the next 50 years! I worry about stress on the sweat joints too. Thanks for your advice!

  • #2
    Re: stress on copper pipe

    A little stress is okay, as does it move that 3/4" with one hand, or do you have to pound a wood wedge to get it to move? Notching the wood or moving the pipe straps sould free up the pipe in most cases to get the adjustment you need.

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    • #3
      Re: stress on copper pipe

      adding stress to the pipes may not be bad BUT may cause 'water hammer'. when the pipes are too tight and no room to expand once a fast acting valve shuts.. ie a shower valve.... if you hear banging and or knocking when you shut off your shower u may need to install a water hammer arrestor to take up the 'shock' in the pipes from the quick shutting valve..
      if u cant bedazzle em with briliance, baffle em with bulls&*t

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      • #4
        Re: stress on copper pipe

        This is a tough question to answer, because I've no idea how much stress you're going to create... it depends on the specifics of the installation, where the tube clamps are, etc.

        "Stress" isn't good, but it won't automatically create a failure or even a decrease in reliability... it all depends on "how much". Not trying to be flip about your question... but hopefully you can see that there is no way to provide a responsible answer from the info in your post.

        I've moved pipes a bit to place a drop-elbow at the "right" depth... never had a problem. But then again I've never moved a tube enough that I felt I should worry about it. I've made a living doing engineering calculations but have NEVER computed stress on a piece of copper plumbing (although it would be dirt simple to do) Not a very helpful answer, I know...

        I would worry about the water hammer, which in my experience happens irrespective of whether you stress the tube or not - especially with a shower or for that matter any high flow rate fixture. Washing machines are also especially prone to this because the solenoid valve in the machine shuts the water off very abruptly. Copper and solder are both very strong but neither likes cyclical loading -Fortunately solder, in plumbing, is in joints that are (if done properly) very well supported by the copper so it's performance is excellent. Copper, though, is a material that work hardens... meaning that the more you flex it, the harder and more brittle it becomes, until it cracks. Water hammer is a vibration load... many cycles every time it happens... and so a good thing to avoid. You can buy the water hammer device or in many cases just stub a stack vertically up in the wall with a cap on it. I make the stub 18" vertically and it seems to work... the pro plumbers may comment on what they use (listen to them - I just do what has been working for me). The air trapped in the stub does the trick.

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