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Thread: sitting water in pipes?

  1. #1
    Remodel Contractor GabeS's Avatar
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    Default sitting water in pipes?

    Just out of curiousity, when people put extension pipes in supply lines to prevent water hammer, those extensions eventually fill with water. Can that sitting water go bad? Or does it get replaced with new water? What if it's a long extension that was meant to be used for something but never was and was capped off. Does the water sitting in the pipes become contaminated?
    Gabe

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  2. #2
    Engineer Furd's Avatar
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    While water sitting in pipes for long periods of time can be a breeding ground for bacteria the bacteria has to come from somewhere. Most bacteria that is found in municipal water supplies is harmless to humans.

    I have seen (and smelled) water that had been in wet fire suppression sprinkler lines that was almost black and stank to high heaven. I wouldn't have wanted to drink that water but I don't know if doing so would have necessarily harmful. The same is true of water that had been in a heating system for many years.

    Municipalities will often flush the main lines by opening fire hydrants and letting the water flow for anywhere from a couple of minutes to as much as a half hour or more if the hydrant is at the end of a main line.

    In a residence I don't think there would be any problem from air chambers although if there was a long length of "dead ended" pipe that was for an addition to the house I would probably flush that pipe for several minutes before drinking any water from the end.

    If you have a well please ignore this post.

  3. #3
    Plunger/TurdPuncher kingsotall's Avatar
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    Can you say Legionella┐ I learn a lot from the DIYers on here because they ask questions that I never would have pondered. Waiting intently for further discussion on this thread.

  4. #4
    Engineer Furd's Avatar
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    The Legionella has to come from somewhere. Although I certainly could be wrong I also seriously doubt that you will find Legionella in a municipal water supply. All the cases of Legionella I am aware of were airborne and came from improperly treated cooling towers or stagnant ponds.

    Again, if your water comes from a well, ignore this post.

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Default water

    Comparing inactive water in a potable system to that in a fire line is ludicrous. They are not even close to the same thing, which is why fire systems use multiple anticontamination devices to separate the two.

  6. #6
    Engineer Furd's Avatar
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    Really? I've seen a lot of fire suppression systems and all they had was the automatic sprinkler valve separating them from the potable water system. Maybe they don't do it that way anymore and maybe the ones I saw were grandfathered. At any rate if the fire suppression system is filled with potable water I think the comparison IS valid.

    Even if I am totally nuts about the comparison of fire suppression sprinklers to a dead-ended pipe in a potable water system in a residence, how about giving an answer to the original poster?

  7. #7
    Master Plumber Redwood's Avatar
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    Quote Originally Posted by Furd View Post
    Really? I've seen a lot of fire suppression systems and all they had was the automatic sprinkler valve separating them from the potable water system. Maybe they don't do it that way anymore and maybe the ones I saw were grandfathered. At any rate if the fire suppression system is filled with potable water I think the comparison IS valid.

    Even if I am totally nuts about the comparison of fire suppression sprinklers to a dead-ended pipe in a potable water system in a residence, how about giving an answer to the original poster?
    Fire protection systems are required to have backflow prevention installed. If it has not been enforced in your area inspection is lax. In the picture below the grey device is a backflow preventer.



    Legionella is present in water supplies in low amounts and it is not killed by chlorine in the levels used in water distribution systems. It is not usually a problem unless it spends time in a stagnant location at thr prime growth temperature.

    Dead end lines over a certain length are prohibited by code. Check the code used in your area to determine length. They can present a problem of biological growth in the system.

    You are correct air chambers are ineffective as hammer arestors. The air in the chamber is both absorbed into the water and dispraced by water movement. Piston type hammer arrestors should be used.


  8. #8
    That's all folks! Gary Slusser's Avatar
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    The cause of water hammer is a too high velocity in the pipes. The cause of that is too high pressure. All types of arrestors usually stop working soon or later.

    Dead ends are a bad thing because they can not be sanitized.

    In the last ten to fifteen years there have been many cases of Legionella found in water heaters; city water or not. That has happened since the government made heater manufacturers reduce the temp from 140 to 120.
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