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Thread: Hot Water Heater noises

  1. #1

    Default Hot Water Heater noises

    I'm a fairly new home owner. It's just been a little over a year now. My hot water heater isn't the newest on the block, but I thought I'd ask a few questions before I spent the money and time replacing it. After showers and running the dishwasher the heater makes a lot of "clunking" noises. I don't really lose pressure, or have any leaks. It still seems to heat fairly well. I have it on the lowest setting and I still get plenty of hot water. But the obscene knocking that rattles through the pipes is getting old. Anyone have any ideas?

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    You can try (but it probably won't help) flushing it out a little. Sometimes, you can remove the drain valve and poke a stiff wire or rod in there and crack out some. If it is electric, you can try removing the elements (they're not expensive). Too much poking/proding/banging and you make start a leak. It sounds like you have mineral deposits. These can act like insulators and can have pockets in them. WHen the heater turns on, they can cause localized bursts of steam as things get hot. These can sound like mini explosions and really rattle things. It could last a long time yet, or it could fail soon. You might want to budge for a replacement. The plumbers here recommend Bradford-White or Rheem; avoid the Whirlpool sold at Lowes like the plague. The GE at HD is made by Rheem, and is a decent unit.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3


    If it makes a "snap, crackle, pop" sound whenever the burners are going, then it is indeed a buildup of lime. Draining and flushing the tank can delay the inevitable replacement. Some people even fill the bottom with white vinegar and leave it in there for a day or two before flushing it out.

  4. #4


    It's not a snap or crackle when the elements are shutting off. It's comming from inside the tank. You hear it through the piping in the house. I was actually thinking of making the move to a hot water on demand system. Any thoughts on that?

  5. #5
    Master Plumber Redwood's Avatar
    Join Date
    Dec 2007


    Justin picture this....

    An element encased in a lime deposit instead of being surrounded by water.
    The water is going in there but it is pretty well encased.

    The element turns on and heats the water in this pocket but there is not a lot of circulation so it gets very hot.

    All of a sudden it turns to steam and blows out of there where it promptly cools back of and becomes water. meanwhile fresh water refills the pocket and the cycle repeats.

    These miniature steam explosions are making the banging noises you hear.

  6. #6
    DIY Senior Member Probedude's Avatar
    Join Date
    Nov 2008


    Just an FYI, it may not be lime.
    Only recently did I realize what was happening at the house I used to rent.

    - replaced the gas water heater and though new it soon rumbled a lot.
    - drained the tank and sure enough clear/whitish 'pebbles' would come out.
    - noise subsided for about a month, then started up again. Drain tank and again lots of 'pebbles'.
    - thinking the water must be REALLY hard, I made sure the water softener was okay - it was.

    Now 7 years later after replacing a water heater at my 'new' house I realized that the other house's water heater used an aluminum anode rod! It was the corrosion and debris of the aluminum rod, accelerated by the use of the water softener, that was creating the debris at the bottom of the tank causing the rumbling!

    So it's not just lime that causes water heaters to rumble a lot - my gas one was an example.

    drain some of the water heater volume and see what comes out.

  7. #7


    The whitish stuff you see I'm told is a calcium-magesium silicate. That sound will not go away until you replace it. You can't drain and flush it out completely. New water heater is the only way to get rid of the sound.


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