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Corroded pipe nipple

Discussion in 'Technical Discussion' started by Trak, Jan 14, 2020.

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  1. Trak

    Trak Member

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    This pipe nipple went from my raw water AC pump to the AC compressors. It is brass vs. bronze. Is this due to wear or electrolysis? I replaced with bronze.

    I walked into the engine room and my feet got wet from spraying salt water.

    Attached Files:

    Last edited by a moderator: Jan 15, 2020
  2. Pascal

    Pascal Senior Member

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    You need to have a chat with the idiot who installed this... sadly it s a common mistake I ve seen too many time

    bronze male male nipples are VERY DIFFICULT to find. Usually unavailable at west marine and the like. Are you sure you got a bronze nipple?

    Marelon is a better option than brass
  3. Trak

    Trak Member

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    Yes it is a bronze nipple. I couldn’t find a 3” so I had to use a close nipple. Luckily I had enough hose to fit.
  4. Capt Ralph

    Capt Ralph Senior Member

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    This is NOT a bronze nipple.

    This is an example of a brass fitting. Bronze is preferred.
    It is a hard task to find all correct materials at times when assembling thru hull fittings.
    Sadly, not all correct hardware will be found at discount suppliers without some deep digging.
    Brass or even some red-brass will fail against bronze.
    It's in the noble material scale list..
  5. Trak

    Trak Member

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    I am saying I replaced it with bronze. The one shown in the pic is brass.
  6. Capt J

    Capt J Senior Member

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    I had that situation with a dometic copper A/C discharge tree connected to the a/c pump with a red brass nipple. Did not last a year. The way I fixed it was with a bronze pipe thread to hose barb fitting and another bronze pipe thread to hose barb fitting with a very short piece of hose double clamped in between the two hose barbs. Same length but now bronze on both ends. I can find the bronze to hose barb fittings virtually anywhere. I've never seen a bronze nipple to nipple.

    Most likely electrolysis and erosion.
  7. cleanslate

    cleanslate Senior Member

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    You will never find a bronze pipe nipple like that cause they are not made. They are all brass. There are some bronze close nipples from Groco etc.,that are large for seawater intakes, etc. but no length nipples made in bronze, all brass.
    I do not think the close nipple you just put in is bronze....Good idea what Pascal and Capt J said.
  8. Pascal

    Pascal Senior Member

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    Where did you source the new bronze nipple ?
  9. Capt Ralph

    Capt Ralph Senior Member

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    The brass fitting failed from a dissimilar metal issue from all other materials. Galvanic erosion ate it up the softer material.
    I'm not sure now what you are asking.
    ,rc
  10. Capt J

    Capt J Senior Member

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  11. Capt Ralph

    Capt Ralph Senior Member

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    Please note the prices of bronze vs brass.

    Next question. What's up with the Teflon tape? All material must make an electrical connection. If insulated with some tapes or sealants, the electrical connection may not be solid and a difference of potential (galvanic erosion) may happen.
  12. Capt J

    Capt J Senior Member

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    I use Teflon tape, I find it's worn through in plenty of area and makes a good bond. It doesn't leak, you don't have to he-man tighten it so that it remains leak free...….IDK......

    I've seen most manufacturers use pipe dope on water connections.
  13. Trak

    Trak Member

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    I did buy the Groco bronze close nipple. I did not install the old brass fitting. The new installation also makes metal to metal contact.
  14. Beau

    Beau Senior Member

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    NEVER use brass on any through hull fitting or line, even at its terminal end. It will sink you sooner or later. Brass is best left for clocks and decorative feature above the water line. Safe alternatives are myriad, but all need to be inspected regularly.

    A quick eye check: Bronze will be reddish, brass will be yellowish. Scrape thru the oxidation.

    Also the use of plumbers tape (my term) should be left to a minimum because it can interfere with your galvanic grounding system, and in some case completely isolate the fitting. I'd check that seacock and any other metals in that distribution line Use compression fittings or a tapered thread
    Last edited: Jan 14, 2020
  15. cnvsback

    cnvsback Member

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    Teflon tape does in fact leak, quite often. As of the last ten years the are numerous other pipe sealant options are available in addition to teflon tape. Teflon tape often also acts as an insulator.

    Try Loctite 565

    Engineered for just about any plumbing circuit up to 2'' diameter and under 3,000PSI nominal operating psi, 565 suffices. Including potable water lines not exceeding 180F.
  16. Capt Ralph

    Capt Ralph Senior Member

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    That was a lot of tape on one end. Maybe dope on the far end.
  17. rtrafford

    rtrafford Senior Member

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    Agreed. My technique is to keep the sealant north of the first thread tooth. While I expect the threads amidst the dope to find some contact, I rely on the initial thread to make certain bond. Keep it clean.

    And, yes, always always bronze. Brass will evaporate with the slightest electrolysis.
  18. Oscarvan

    Oscarvan Senior Member

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    Is pipe available? Tapping a thread on it should be easy considering how soft it is.
  19. Marblehead01945

    Marblehead01945 Member

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    I'm dealing with corrosion as well. Nasty stuff. Sourcing this for replacement.

    Attached Files:

  20. Beau

    Beau Senior Member

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    Interesting. Is that outlet (?) always beneath the water line as it appears. If so, I think it would need to be bonded or otherwise protected with a zinc.