[APD] RE: Re: pH at which CaCO3 dissolves--Ca deposition on heaters

["Cheryl Trine" <ctrine at andrews_edu>]

Douglas Guynn wrote:


>I believe the answer to your question lies in a property know as "scaling
>tendencies".

Douglas, Thank you for your explanation.  Your answer sounds logical to me.
I was under the impression that increased temperature increases solubility,
so I couldn't understand why the scale should be building up over the
heating elements and not on other surfaces in the water.  (Yes, I do get
deposition at the water line, but I figured that's to be expected because of
evaporation).

I also appreciate your identifying possible solutions.  Because my water is
so hard, I think it would require the use of RO/DI to solve the problem with
water changes.  I think my best bet would be to use smaller heaters.
Although I'm only using 5 watts/gallon, perhaps it would be better to use 2
heaters with half the wattage.  That way the heating elements wouldn't get
so hot.

For those who want to know more about my situation, I use both hang-on-the
back and submersible glass heaters (Ebo Jaeger, etc.)  The deposits form
over the heating elements.  My water has a pH = 8.2, KH = 300 ppm, GH = 320
ppm.  I would expect most of the hardness is due to calcium because the
municipal water supply comes from wells, and the underlying rock is
fossiliferous limestone.  Don't know what the TDS values are, but 25-50% of
the water is changed every week.

Thanks again for your detailed explanation of scaling.

Cheri

 

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