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Thread: Abandoned line in wall; stagnant water a concern?

  1. #1
    DIY Senior Member speede541's Avatar
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    Default Abandoned line in wall; stagnant water a concern?

    I'm installing a bunch of copper that serves current fixtures, but also runs to locations of planned fixtures.

    Nearly every current fixture will disappear, and the abandoned stub that I'll cap will stay connected to the branch line continuing on to the future fixture location.

    Under this scenario, is there any concern with stagnant water entering the branch? The abandoned lengths will be limited to a foot or two at most, and all connect vertically above the in-service branch. This is all bathroom and laundry service, for what it's worth.

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    In the Trades Gary Swart's Avatar
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    I can't see how that water will be stagnant if it is still connected to the water supply. Does water become stagnant in a water line that is not used often? I don't think so. In the interest of neatness, I might try to cut the stub as short as possible, but not to prevent stagnation.

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    DIY Senior Member craigpump's Avatar
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    I would remove the old pipes. Bacteria from stagnant water or from working on the plumbing can "hide" at the end of those runs and could potentially contaminate your water supply. Treating/killing the bacteria will be tough because the water won't flow back into those stubs.

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    DIY Senior Member kreemoweet's Avatar
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    Quote Originally Posted by craigpump View Post
    I would remove the old pipes. Bacteria from stagnant water or from working on the plumbing can "hide" at the end of those runs and could potentially contaminate your water supply. Treating/killing the bacteria will be tough because the water won't flow back into those stubs.
    What a ridiculous statement. It is the RARE water supply system that doesn't have numerous "dead ends" in both the supply pipes and fixtures, and there is no
    danger from "stagnant" water (whatever that's supposed to mean) or from nonexistant "bacteria". There is little to nothing in modern water supply systems to support
    the growth of microorganisms, and of course the water has usually been treated with chlorine and other disinfectants. If you're piping skunk water into your house from
    some nasty pond in the back woodlot, then you might have something to worry about.

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    Forum Admin, Expert Plumber Terry's Avatar
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    The abandoned lengths will be limited to a foot or two at most
    I don't see any problems with that.

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    DIY Senior Member craigpump's Avatar
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    @ Kreme, I see it all the time when a well is chlorinated and someone doesn't get chlorine through the entire system. That one little obscure spigot or delivery to a humidifier can harbour coliform bacteria that can/will reproduce and re contaminate a water supply.

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    DIY Senior Member speede541's Avatar
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    Quote Originally Posted by kreemoweet View Post
    there is no danger from "stagnant" water (whatever that's supposed to mean)
    stag·nant: Adjective
    (of a body of water or the atmosphere of a confined space) Having no current or flow and often having an unpleasant smell as a consequence.
    Showing no activity; dull and sluggish: "a stagnant economy".

    I've seen the insides of old pipes and they're far from pristine. Not saying it's bacterial infestations, but I don't want to drink it. Hence my question.

    I get what your saying about "dead ends" existing in a system, but I'm betting that water doesn't see any movement, i.e. stagnant. I'll roll with it, though.


    Quote Originally Posted by Terry
    I don't see any problems with that.
    Great, thanks.

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