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Lots of scale -- is it the water or the heater?

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DCContrarian
DCContrarian Member Posts: 120
edited April 15 in Domestic Hot Water
I have a heat pump water heater for the first time in my life. It's in a new house. It was installed about 18 months ago. About six months ago one of the heating elements burned out, when I drained the tank to replace it I noticed there was an unusual amount of scale in the drain water. I figured I'd better check back in six months. That was today. Attached are pictures of the element and what was in the drain water.




While I had the elements out I shined a flashlight through one hole and peeked in through the other. The dip tube and the anode both looked like stalactites, but the anode did not seem to be eroded.

My question is, is this just a symptom of what my water is like, or is there something about heat pumps? At this point I'm resigned to just flushing the tank every six months.

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  • hot_rod
    hot_rod Member Posts: 22,256
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    Usually the elements only scale if they are being used. The hot metal surface attracts the minerals in your water. Do you know if the elements are kicking on to boost production, often? Ideally you could run 100% in HP only mode.

    The mineral precipitation will be directly related to the water hardness and TDS total dissolved solids

    If you have hard water the options are a softener or a treatment like TAC.

    I believe HPWH have a coil wrapped around the outside of the tank, so the scale will not be as much an issue as it is in gas fired type heaters, where it settles on the bottom and limits heat transfer.

    No harm in flushing the tank occasionally.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Larry Weingarten
  • Intplm.
    Intplm. Member Posts: 2,006
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    It's not something about heat pump water heaters. Regular electric water heaters can have similar reactions to water, which is what your water heater is experiencing.

    The rice stone/pebbles are common. I have had some water heaters with as much as two feet or more of those stones in an electric water heater.

    Draining, or flushing twice a year might be unnecessary. You will know how often flushing is needed via. trial and error over time.
    FYI:
    Bradford White water heaters have a type of patented swirling action that can help prevent mineral build up at the bottom of the water heater.
  • DCContrarian
    DCContrarian Member Posts: 120
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    Intplm. said:


    Bradford White water heaters have a type of patented swirling action that can help prevent mineral build up at the bottom of the water heater.

    Isn't it better to have the build-up in the bottom of the water heater and flush it out once or twice a year than to have it flow into the piping and clog the fixtures?

  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,094
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    Intplm. said:


    Bradford White water heaters have a type of patented swirling action that can help prevent mineral build up at the bottom of the water heater.

    Isn't it better to have the build-up in the bottom of the water heater and flush it out once or twice a year than to have it flow into the piping and clog the fixtures?

    That will depend on the size of the particle that is being suspended in the water. Those pieces of scale in your photo are thousands of microscopic pieces of material that will join together to form a larger piece of scale. If you can get rid ir that stuff before it grows too big then you will not clog up fixtures. Then there is less scale to worry about.

    And I believe that swirl is not in every water heater but is a function of the dip tube design.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    Intplm.
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,335
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    Hi, Looking at the scale, it tells two things. First is that the brownish stuff is hardness that fell from the element. It suggests that the heat pump isn't working very well, or that the tank is undersized for your usage. The bluish stuff is corrosion from an aluminum anode rod. It's a neurotoxin, so not good to ingest. I'd replace the anode with a magnesium one or a powered rod.

    Yours, Larry
    hot_rod
  • Derheatmeister
    Derheatmeister Member Posts: 1,549
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    Are you on your own well or is your water supplied via municipal water/Treated ?
  • DCContrarian
    DCContrarian Member Posts: 120
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    Are you on your own well or is your water supplied via municipal water/Treated ?

    City water, Washington, DC.
  • Derheatmeister
    Derheatmeister Member Posts: 1,549
    edited April 16
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    Are you on your own well or is your water supplied via municipal water/Treated ?

    City water, Washington, DC.
    Can you obtain a water Quality report from your supplier ?

    High TDS/Water hardness are probaly the source of your issues which can be addressed via localized watertreatment such as a water softener (Not a big fan) a Scale transformer or other Methods.
    Since the Flint Michigan incidence some of the Municipal water suppliers have artificially brought the PH of the water up in order to prevent loosing the Patina from the inside of the piping system.
    Patina such as copper Oxide(CU2O) is a protective layer that helps prevent Lead from leaching into our drinking water !
    When teaching a Class in Denver regarding hydronic system fluid maintenance it became very obvious that the PH and TDS was very high when we sampled and tested the Domestic water supplied to the Building.
    Also: In Talking to some of the trades we have also seen accelerated in increase in waterheaters failures which IMO is partially due to some of the things mentioned above.