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  1. #1
    Tom Anderson's Avatar
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    Default Clear PEX tubing turning black

    Attached photo of 5 year old home water system showing cold water clear PEX turning black. Hot water lines not involved. Municipal Water Co. says trace amounts of Iron and Manganese causing PEX to turn black.
    Perhaps hot water heater anode or heat is causing dispersion.
    Can anyone identify exact causative factor?

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    Default Re: Clear PEX tubing turning black

    Quote Originally Posted by Tom Anderson View Post
    Attached photo of 5 year old home water system showing cold water clear PEX turning black. Hot water lines not involved. Municipal Water Co. says trace amounts of Iron and Manganese causing PEX to turn black.
    Perhaps hot water heater anode or heat is causing dispersion.
    Can anyone identify exact causative factor?
    Clear PEX for potable water system?? (oxygen doesn't transfer/diffuse through clear tubing?/how does it block light?) I have to admit, the idea of clear tubing exposed to light as pressurized potable water supply is a new one on me! (drain maybe, radiant maybe (air issues?) but POTABLE???). Does NH have codes now for residential (or ag) building, mechanical and plumbing state-wide?

    As far as accumulations within I don't find the anode theorty entirely plausable as causal but perhaps indicative of another process.

    Namely, biofilm/bioslime from aerobic (possibly aneorbic) bacteria and possibly other organisms (protozoan, ameboa, algae, other).

    Whether iron reducing, sulfur reducing, e-coli, or a host of other contaminates the biofilm doesn't belong, and if potable not heating system could be dangerous to health.

    Potential sources of contamination include water supply itself, water treatment system, backflow from hose bib, no check or backflow preventor/vacuum breaker to irrigation system, etc., FAILURE TO DISINFECT WATER SYSTEM WHEN INSTALLED and prior to connection to a clean supply, and a host of others (such as cross contamination with DWV elsewhere in system, syphoning (such as faucet not above flood rim or syphoning ball cock in toilet, inconsistant positive water pressure, etc.), ground water runoff, septic or sewer contamination of private well or breach in water supply line, etc.).

    Black slime deposits on plumbing supply usually contamination. Chlorine based disinfection is not generally effective for biofilm, usually requires hydrogen peroxide and/or quat.

    The only way I can think of to properly diagnose would be to have a certified lab review a section of the "clear pex" and analyize the deposits or film/slime at the same time multiple water samples are analyized.

    Last edited by H.G. Watson, Sr.; 12-02-2009 at 12:14 PM.

  3. #3
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    Default Re: Clear PEX tubing turning black

    Tom,

    If the Water Source was The problem then All of the Plumbing Fixture Supply Lines would show a similar degree of buildup.
    .
    Your Photo shows varying degrees of discoloration several almost totally black while others have none to little.
    .
    I would suspect a Back Flow condition exists on the Discolored Supply Lines.
    .

    It Might have Choked Artie But it ain't gone'a choke Stymie! Our Gang " The Pooch " (1932)
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  4. #4
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    Default Re: Clear PEX tubing turning black

    Some of the lines also look like they have a "Pink" tint, most of those are on the right side or I'm guessing the hot water side.

    Any idea what brand pipe was used? It should have the brand and an ID number printed on the pipe.

    I would most likely tell them to get a water quality expert to test and figure out. Dissolved minerals can cause some strange discolorations to plumbing lines and fixtures. Many times the hot water side will not experience the same problems due to the heating of the water and sometimes the anode rod in the tank. When water is heated with some dissolved minerals the minerals tend to attach to each other and sink in the tank to the bottom or attach to the anode rod. On the other hand, some dissolved minerals show up more on the hot water side of a system.

    It is one of the times that you should not be upset by saying, "I don't know".

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  5. #5
    Tom Anderson's Avatar
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    Default Re: Clear PEX tubing turning black

    I have sent the photo's to a friend at the State for his advice. Here is a photo of the PEX. The initial homes built in 2005 had clear PEX then a shift to opaque red and blue. Perhaps someone knew something.

    Last edited by Tom Anderson; 12-02-2009 at 01:25 PM. Reason: adding photo

  6. #6
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    Default Re: Clear PEX tubing turning black

    sorry here is photo with ID

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  7. #7
    Bruce King's Avatar
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    Default Re: Clear PEX tubing turning black

    I have seen that on one house with the "clear" pipe with well water supply.
    The picture shows a dark blue color which is the same as what I saw before. Did it look black? Makes you wonder what we would see if more of the clear was used instead of blue and red.

    Bruce King, B.A. King Home Inspections, LLC
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    Default Re: Clear PEX tubing turning black

    Quote Originally Posted by H.G. Watson, Sr. View Post
    Clear PEX for potable water system?? (oxygen doesn't transfer/diffuse through clear tubing?/how does it block light?) I have to admit, the idea of clear tubing exposed to light as pressurized potable water supply is a new one on me! (drain maybe, radiant maybe (air issues?) but POTABLE???). Does NH have codes now for residential (or ag) building, mechanical and plumbing state-wide?

    HG,

    Wirsbo AquaPEX is the PEX tubing that I see most often around here. Not exactly clear, more translucent. Yes, potable.

    Uponor - Plumbing Systems

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  9. #9
    Tom Anderson's Avatar
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    Default Re: Clear PEX tubing turning black

    Now that you mention it it does look very dark blue


  10. #10
    Ed Mario's Avatar
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    Default Re: Clear PEX tubing turning blackish or bluish...

    Hello, my hot water return lines to the holding tank from my sinks are turning blackish or bluish in color. The lines are clear WIRSBO PEX the system is about 4 years old, never saw this before. I found a thread posted some years ago about this very issue along with possible causes. However none of the posts had a clear conclusion on a cause or how to rectify the problem. Any additional info related to this issue is greatly appreciated.

    Many thanks -Ed


  11. #11
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    Default Re: Clear PEX tubing turning black

    I know this post is a little old, but I just ran across it. It appears that the tubing is being used in a hydronic heating system, one problem being that the tubing is Aquapex, Uponor's trade name for their potable water pex. It has no oxygen barrier, and is not rated for hydronic applications.

    The discoloration is likely due to the corrosion of ferrous materials in the system; cast iron pumps, unlined expansion tanks, iron body fill valves, etc...

    I'm glad this isn't my house. There will be serious problems down the road.


  12. #12
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    Default Re: Clear PEX tubing turning black

    Quote Originally Posted by Steve Truesdale View Post
    I know this post is a little old, but I just ran across it. It appears that the tubing is being used in a hydronic heating system, one problem being that the tubing is Aquapex, Uponor's trade name for their potable water pex. It has no oxygen barrier, and is not rated for hydronic applications.

    The discoloration is likely due to the corrosion of ferrous materials in the system; cast iron pumps, unlined expansion tanks, iron body fill valves, etc...

    I'm glad this isn't my house. There will be serious problems down the road.
    Interesting theory, however, the labeling clearly indicates distribution as to potable system, i.e. "master bath sink, 2nd bdrm bath sink, kitchen sink, etc.".

    Agreed would be inappropriate to utilize for hydronic, as would sourcing heated water from a WH in NH for same (s/b a boiler).


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