knocking noise as in hot water tank

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by kskier, Sep 4, 2007.

  1. kskier

    kskier Home Handyman

    Sep 4, 2007
    Home Handyman
    Buffalo NY
    I recently drained my hot water tank, and while I was doing that, I had to reroute some plumbing, to make it easier to get at my furnace. After I got plumbing done, and water back into tank, every time hot water is used, and as it is heating up, it starts making poping sound inside tank. It only happens when water is being heated up. The manufaturer said that tank might have built up inside tank. The tank is about 6 years old. After water is heated up,,,,,and tank sits for a bit, no noise is heard. Any thought's??
  2. jimbo

    jimbo Plumber

    Aug 31, 2004
    San Diego, CA
    Not sure why it would be related to the work you did, but as tanks develop a heavy mineral deposit in the bottom, what happens is that you get water actually boiling in a localize pocket between the metal tank pocket, and the mineral slab. At some point, the "bubble" pops, and that is the popping noise you hear.
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  4. CHH

    CHH New Member

    May 25, 2007
    Denver, CO
    My thoughts are: the manufacture is likely correct. Mineral deposits create heat transfer problems that result in poping noises. Six years might be getting pretty far along in the life of the water heater depending on the local water quality. No reason to replace it just 'cause it is making a little noise but it is one indication that the heater is getting older in terms of function (if ya get my drift).
  5. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona

    The popping noise is water inside little rust nodules inside the tank, usually on the center flue. The water turns to steam, is forced out of the nodule, and then condenses back to water with a mini explosion as the latent heat is released. Eventually the water heater will start leaking when one of those rust areas penetrate the tank, but until then there is no reason to worry about them because you cannot cure them.
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