• Please visit and share your knowledge at our sister communities:
  • If you have not, please join our official Homebrewing Facebook Group!

    Homebrewing Facebook Group

How to guess your waters Ca++ and Mg++ if all you know is its hardness

Homebrew Talk

Help Support Homebrew Talk:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Silver_Is_Money

Larry Sayre, Developer of 'Mash Made Easy'
Joined
Dec 31, 2016
Messages
6,462
Reaction score
2,226
Location
N/E Ohio
If all you know with regard to your water is its total hardness, you can make an educated guess at determining its approximate ppm Ca++ and Mg++ ion concentrations 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

Therefore:
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
 
Back
Top