Alkalinity as CaCO3 and Total Hardness as CaCO3

Discussion in 'Homebrewing' started by OldBrewer, Feb 26, 2020.

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  1. OldBrewer

    OldBrewer Maven (1,385) Jan 13, 2016 Canada (ON)

    I'm trying to understand water chemistry a little better, and am confused between "Total Alkalinity as CaCO3" and "Total Hardness as CaCO3".

    Other than Calcium, Magnesium, Sodium, Sulfate and Chloride, my water report only provides "Total Hardness as CaCO3" (and also the pH, which is less than 8.4). Is this the same value as "Total Alkalinity as CaCO3"? If not, is there a formula that will calculate "Total Alkalinity as CaCO3" from "Total Hardness as CaCO3"?

    Thanks.
     
    #1 OldBrewer, Feb 26, 2020
  2. Silver_Is_Money

    Silver_Is_Money Devotee (337) Jun 4, 2017 Ohio

    This works for units of ppm (mg/L):

    Total Alkalinity (as CaCO3) ~= 50.0435(Ca/20.039 + Mg/12.153 + Na/22.99 - Cl/35.453 - SO4/48.031)
     
    #2 Silver_Is_Money, Feb 26, 2020
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  3. VikeMan

    VikeMan Grand Pooh-Bah (3,067) Jul 12, 2009 Pennsylvania
    Pooh-Bah

    Does your report by any chance list "(Total) Alkalinity as HCO3"? Or simply "(Total) Alkalinity"? In other words, does the word Alkalinity appear anywhere?

    The formula @Silver_Is_Money should get you in the ballpark for many/most water sources, but note that if there are other conservative cations/anions present, they could affect the actual alkalinity. (Or maybe better stated, they would infer the presence (or absence) of balancing ions such as HCO3, CO3, etc., which is where alkalinity comes from.)
     
    #3 VikeMan, Feb 26, 2020
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  4. Silver_Is_Money

    Silver_Is_Money Devotee (337) Jun 4, 2017 Ohio

    Yes, the primary error in my formula is in that it does not include the generally more minor ions such as those of iron, potassium, nitrate, fluoride, manganese, etc...

    For more precision they can be added, but generally (on first guess) they may only move the final answer by about +/- 5% (though occasionally by more).
     
    #4 Silver_Is_Money, Feb 26, 2020
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  5. OldBrewer

    OldBrewer Maven (1,385) Jan 13, 2016 Canada (ON)

    No, the report does not list alkalinity in any form, just hardness. The reason I wondered why hardness might be converted to alkalinity in some manner is because the Bru'n Water utility has a 'Water Report Input' section where you input the water report data. In the 'Alkalinity Conversion Calculator', it says to input: "Reported Total Alkalinity or Temporary Hardness (as CaCO3) (mg/Lor ppm)". Since either can be entered, it seems to suggest that "Temporary Hardness" is identical to "Total Alkalinity". Thus I assumed there must be some formula that connects Total Hardness to Total Alkalinity.
     
    #5 OldBrewer, Feb 26, 2020
    Last edited: Feb 26, 2020
  6. OldBrewer

    OldBrewer Maven (1,385) Jan 13, 2016 Canada (ON)

    Thanks, Silver_Is_Money. That should do the trick in the absence of direct alkalinity data. Being within 5% is much better than having no estimate at all. I have contacted our Water Department again to see if they may have missed reporting the alkalinity data previously.
     
    #6 OldBrewer, Feb 26, 2020
    Last edited: Feb 26, 2020
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