If all you know with regard to your water is its total hardness, you can make an educated stab at determining its ppm Ca++ and Mg++ ion concentration as follows:
First, convert whatever units your total hardness is reported in into units of ppm (mg/L) of total hardness "as CaCO3".
Next, it appears as if an aggregate average of all of the worlds fresh water indicates that "on average" roughly 70% of fresh waters "total hardness" is derived from Calcium, with roughly 30% from Magnesium.
MW of CaCO3 = 100.0869
MW of Ca++ = 40.078
MW of Mg++ = 24.305
100.0869/40.078 = 2.4973
100.0869/24.305 = 4.118
Total Hardness (as CaCO3) = 2.4973(Ca++) + 4.118(Mg++)
Therefore, on average:
Ca++ ~= (0.70*TH)/2.4973
Mg++ ~= (0.30*TH)/4.118
How to guess your waters Ca and Mg if all you know is its Hardness
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How to guess your waters Ca and Mg if all you know is its Hardness
Developer of 'Mash Made Easy', a free and complete mash pH adjustment assistant spreadsheet
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Re: How to guess your waters Ca and Mg if all you know is its Hardness
You could check if this is correct by entering the same information into Graham's calculator on this forum.
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1. Life is not a journey to the grave with the intention of arriving safely in a pretty and well-preserved body, but rather to skid in sideways, thoroughly used, totally worn out and loudly proclaiming... "f*ck, what a trip
It's better to lose time with friends than to lose friends with time (Portuguese proverb)
Alone we travel faster
Together we travel further
( In an admonishing email from our golf club)
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Re: How to guess your waters Ca and Mg if all you know is its Hardness
It will never be "correct" sans for blind luck. But it is fairly close often enough. All it can tell you is that if your water is "average" for its given level of total hardness this is what its calcium and magnesium levels would be. But individual sources of water are rarely "average" in their mineral makeup. That said, if it was all I had to go on, I'd brew with it (if I also knew my waters alkalinity).
An inexpensive fish tank GH/KH water testing kit will give you both GH (Total Hardness) and KH (alkalinity).
If, OTOH, you know your actual Ca++ ppm value, the formula seen above can be solved for actual Mg++, or visa-versa.
But to answer your question, if you were to enter the Ca++ and Mg++ figures derived from the formula seen above, the Total Hardness should indeed match the Total Hardness value as seen for the Graham Wheeler calculator.
Developer of 'Mash Made Easy', a free and complete mash pH adjustment assistant spreadsheet
https://mashmadeeasy.yolasite.com/
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Re: How to guess your waters Ca and Mg if all you know is its Hardness
United Utilities and probably most other suppliers post a water report on their website, it has the details. I usually use the rolling average in my calculations, my supply is very consistent so it's a reasonable choice.
It's worth checking your suppliers site.
Atb. Aamcle
It's worth checking your suppliers site.
Atb. Aamcle