Results 1 to 17 of 17
  1. #1
    Join Date
    Apr 2008
    Location
    McKinney Texas
    Posts
    475

    Default CORROSION ON HOT WATER SIDE ONLY?

    From todays inspection: Note the PEX manifold has oxidation on each of the metal fittings for each of the hot water branch lines, while the cold water blue PEX fittings do not have corrison. Oxidation only on the hot water lines. Still trying to sort this out but as to root cause. Anyone have an idea as to why oxidation on the hot side only?

    Similar Threads:
    ***IMPORTANT*** You Need To Register To View Images ***IMPORTANT*** You Need To Register To View Images
    F.I.R.E. Services

  2. #2
    Join Date
    Mar 2007
    Location
    Orlando, FL
    Posts
    1,340

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    Zurn has a spotty history with PEX fittings, including "dezincification" that causes corrosion and "stress corrosion cracking" that causes leaks and corrosion. Google it when you have time, there's plenty to read on Zurn and poor quality brass. Maybe there's a correlation to water temperature as well.

    Dom.


  3. #3
    Join Date
    Oct 2010
    Location
    Southwest US
    Posts
    585

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    Chemical reactions (including oxidation) speed up with heat. was there a water softener in the home?


  4. #4
    Join Date
    Apr 2008
    Location
    McKinney Texas
    Posts
    475

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    No water softner or any other water treatment. Just regular city water.


  5. #5
    David Bell's Avatar
    David Bell Guest

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    Looking at the manifold, the top hot valve has no staining except at the connection to the manifold leading me to believe there was a leak the soaked the rest of the valves.


  6. #6
    Join Date
    Oct 2010
    Location
    Southwest US
    Posts
    585

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    Quote Originally Posted by David Bell View Post
    Looking at the manifold, the top hot valve has no staining except at the connection to the manifold leading me to believe there was a leak the soaked the rest of the valves.
    Bet you're right on that!


  7. #7
    Join Date
    Oct 2008
    Location
    Portland, OR
    Posts
    33

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    (Long shot) Hydronic heating systems can cause corrosion from oxygen concentration but it's pretty much limited to closed loop systems with ferrous metal components and non-oxygen barrier pex.


  8. #8
    Join Date
    Dec 2009
    Location
    Florida
    Posts
    552

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    Quote Originally Posted by Gene South View Post
    From todays inspection: Note the PEX manifold has oxidation on each of the metal fittings for each of the hot water branch lines, while the cold water blue PEX fittings do not have corrison. Oxidation only on the hot water lines. Still trying to sort this out but as to root cause. Anyone have an idea as to why oxidation on the hot side only?
    Gene, with reference to Kyle's comment "(Long shot) Hydronic heating systems can cause corrosion from oxygen concentration but it's pretty much limited to closed loop systems with ferrous metal components and non-oxygen barrier pex.," did you notice any deterioration of the hot water lines at the far end (sink, etc.if visible)?


  9. #9
    Join Date
    Jan 2011
    Location
    Marietta, Georgia
    Posts
    93

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    Gosh, my guess is simply that the hot water lines are condensing moisture when trapped inside this wall cavity and is probably only occurring during certain months. It looks like it's in a basement and the foundation wall is close by, there is no moisture barrier on the foundation wall, no insulation nearby and perhaps it's just condensation on the hot side...I would not lose any sleep over this one unless it is condensing moisture enough to drip onto the floor and framing below and cause staining on the finished material.


  10. #10
    Join Date
    Oct 2010
    Location
    Southwest US
    Posts
    585

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    Quote Originally Posted by Michael Bronner View Post
    Gosh, my guess is simply that the hot water lines are condensing moisture when trapped inside this wall cavity and is probably only occurring during certain months. It looks like it's in a basement and the foundation wall is close by, there is no moisture barrier on the foundation wall, no insulation nearby and perhaps it's just condensation on the hot side...I would not lose any sleep over this one unless it is condensing moisture enough to drip onto the floor and framing below and cause staining on the finished material.
    You need to think about that answer


  11. #11
    Join Date
    Dec 2007
    Location
    Holladay, UT
    Posts
    565

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    Gene, Did you notice if the hot water from tap had a smell to it. I ask because I think Benjamin was on to something with his oxidation theory. I know we all just guess but that is one of the fun parts of this forum. It's interesting to hear all the different theories. It gets your mind going.

    Tom Rees / A Closer Look Home Inspection / Salt Lake City, Utah

  12. #12
    Rod Corwin's Avatar
    Rod Corwin Guest

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    I noticed each of the nuts on the handles are progressively rustier from top to bottom. When those lines are cold condensation builds on them during humid months. Top valve deals with its own condensation. His lower neighbor deals with his own and his buddy above. The one on the bottom gets 8 neighbors dripping on him. So each is progressively wetter. Add heat increase oxidation increased moisture worse at bottom than top. That in combination with poor quality brass as previously stated is whats causing this. Just a hypothesis.


  13. #13
    Join Date
    Apr 2008
    Location
    McKinney Texas
    Posts
    475

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    Guys, the manifold is not in a basement and this is a dry environment (Texas). We generally don't have humidity build up or condensation on water lines, and there did not appear to be any leak. My guess the hot water has speeded up the dezincification process. See the first response by Dom and research PEX fitting issues with dezincification. My guess that is the issue.


  14. #14
    Join Date
    Jul 2008
    Location
    Snowbird (this means I'm retired and migrate between locations), FL/MI
    Posts
    4,086

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    Quote Originally Posted by Gene South View Post
    Guys, the manifold is not in a basement and this is a dry environment (Texas). We generally don't have humidity build up or condensation on water lines, and there did not appear to be any leak. My guess the hot water has speeded up the dezincification process. See the first response by Dom and research PEX fitting issues with dezincification. My guess that is the issue.
    #1 Suspect the "guest bathroom" doesn't get a lot of use, especially enough to regularly flush the HOT water line - stagnant water after having traveled through WH concentrated agressive 02 issues - plumbing dead end. Cold valve pictured dirty finger marks - possibly replaced already by plumber who didn't wipe hands.

    Storage type water heater? How old? If so, pull the anode and inspect, likely time to replace it. Zinc sacraficing. What's the water quality?
    Also as mentioned - stressors when no demand cools, when demand hot water running through heats up, when not used...cools down again. Treated (chlorine residuals, concentrated minerals, etc.) heated water more aggressive. Bad (brass mix wrong) valves and wrong handles/nuts.

    Last edited by H.G. Watson, Sr.; 01-11-2012 at 07:15 PM.

  15. #15
    Join Date
    Mar 2008
    Location
    Charlotte NC
    Posts
    2,303

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    Looks more like the type of corrosion found on battery terminals. Is the water heater electric? Did you test for voltage? Could be a leaking element.

    The beatings will continue until morale has improved. mgt.

  16. #16
    Join Date
    Apr 2008
    Location
    McKinney Texas
    Posts
    475

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    Hello H.G. and Vern. Good input from both of you, thanks. The water heater was natural gas and 7 years old if I recall. I think H.G. is getting close to figuring it out. Water is hard water with high minerals. All those things likely figure in. Anyway, thanks again.

    Gene


  17. #17
    Stephen G's Avatar
    Stephen G Guest

    Default Re: CORROSION ON HOT WATER SIDE ONLY?

    I dont think the fittings are the same material on both side. So it might be galvanic welding (shock), or disimiliar metal welding.
    The parts on the left are reacting badly and creating premature oxidization and the nut is acting like a anode and taking the hit for the team.
    Scrape up that hot fitting and see if its brass or white metal.

    Last edited by Stephen G; 01-24-2012 at 04:52 AM. Reason: words missing, spelling,

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •