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Old 12-05-2012, 04:05 PM   #1
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Default Bicarbonate from Total Alkalinity

I am really hoping someone can help me with this! I am entering my local water profile into Beersmith and I am missing a few fields. I had my water tested at a local, professional, lab and have the water report. I have data for Total Alkalinity and pH, as well as hardness, chloride, SO4, calcium, and Sodium. There was no data for magnesium. My question is, how do I properly calculate bicarbonate from the parameters I have? I have looked on several forums and seem to get different answers every where I look. Any and all help on this issue is greatly appreciated!


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Old 12-05-2012, 04:41 PM   #2
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From what I understand, unless the pH of you water is extremely high (above 8.5 or so) then you can assume almost all of the total alkalinity is in the form of bicarbonate. Note that if alkalinity is reported as CaCO3 then you need to multiply that number by 1.22 to get the bicarbonate concentration.

You can also calculate the magnesium concentration if you want using the equation:

Hardness as CaCO3 = 2.5[Ca2+] + 4.1[Mg2+]


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Old 12-05-2012, 05:23 PM   #3
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Thanks for the reply! The pH here is 8.71. The total alkalinity is reported as 185 mg/L but it isn't specified if that is CaCO3, but I am assuming it is. The same goes for hardness, they did not specify on many of the parameters, but again, I will assume hardness as CaCO3. Thanks again for your help!
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Old 12-05-2012, 05:44 PM   #4
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Well at that pH you'll start getting some carbonate in addition to bicarbonate (but it will still be largely bicarbonate). I'd recommend downloading a copy of Bru'n Water (https://sites.google.com/site/brunwater/). It has a calculator there that will give you the carbonate/bicarbonate concentrations given the pH and alkalinity (and calculate most everything else you'll need to calculate for your water).

That's a fairly high alkalinity which will need to be reduced for most beer styles. If you post the full water profile I'm sure someone will chime in with more specific advice about what to do with the water.
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Old 12-05-2012, 06:01 PM   #5
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Does your city publish a water report? Check it out on line or call them. They are required to check for certain things. I think Mg is one.
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Old 12-05-2012, 06:05 PM   #6
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Thanks again bdh. HbgBill, they do but it only includes data for contaminants and additives, such as chlorine.
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Old 12-05-2012, 08:15 PM   #7
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As bdh said, there is a conversion calculator on the Water Report Input page of Bru'n Water. That will provide the values you need for your other program. Since the pH is a little high, there will be a little CO3 along with the HCO3. I would just plug in the reported alkalinity and a lower water pH that will give you the result as virtually all HCO3. That can then go into any water program.
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Old 12-06-2012, 01:49 PM   #8
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If you copy this

((((((-0.0591384*pH + 3.11647)*pH - 70.2631)*pH + 878.007)*pH - 6565.02)*pH + 29368.026)*pH - 72780.088)*pH + 77220.723

into a spreadsheet cell and replace 'pH' with the name of a cell which contains a pH value between 5 and 9.5 (or declare a variable named 'pH') the cell containing this polynomial will evaluate to the number of mg/L bicarbonate for a solution of alkalinity 100 ppm as CaCO3 (titrated to end point 4.3). The attached graph shows calculated values, the polynomial fit to them and the residuals. It also clearly shows the 'flat' region (between, say, pH 6 and 8.3) where 61*alk/50 is reasonably accurate.
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Old 12-11-2012, 06:57 PM   #9
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A.J's reply is correct. But in the context of brewing water calculators you need to know that most of them ask for bicarbonate to calculate alkalinity. And since most of them are using the simple "alkalinity = bicarb * 50 /61" formula you should calculate bicarbonate as "alkalinity * 61/50" when your water calculator asks for bicarbonate. To be correct, water calculators should ask for alkalinity *or* bicarbonate and pH.

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Old 12-12-2012, 07:55 PM   #10
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Thanks a bunch everyone, you all helped me out tremendously!


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