# General Hardness Tutorial (Sorry Long)

Ok!
I am biting the bullet.
I have pulled out my periodic table, blown the dust off and with grim
determination settled in to finally figure out out this general hardness
stuff.  Actually it didn't seem too hard if I am understanding it
correctly.  But that is where you come in (if you chose to accept this
mission).  I need someone to take a look at what I have scratched out.

Here it goes:

1 degree GH = 18 ppm CaCO3 = 18 mg/L CaCO3 = 18 mg/L MgCO3
(I assume its the same for mg/L for Mg.) ???

Now to convert that to mg/L of calcium only we go to the periodic table
and look up the atomic weights as follows:

Ca = 40
CaCO3 = 40 + 12 + 16*3 = 100

Therefor
1 degree GH = (18 mg/L of CaCO3) * (40 units Ca) / (100 units CaCO3)
= 18 * 40 / 100 mg/L of Ca
= 7.2 mg/L for Ca

Similarly
Mg = 24.3
MgCO3 = 84.3

Therefor
1 degree GH = (18 mg/L of MgCO3) * (24.3 units Mg) / (84.3 units CaCO3)
= 18 * 24.3 / 84.3
= 5.2 mg/L for Mg

Now if I look to my water chemistry:
Water Supply Analysis (City of Winnipeg)
Total alkalinity	78 mg/L
Total Hardness		76 mg/L
pH			8.0
Calcium			20.6 mg/L
Magnesium		5.62 mg/L

I can calculate the GH as follows
Calcium: 20 mg/L / 7.2 mg/L/degree GH = 2.86 degrees GH
Magnesium: 5.62 mg/L / 5.2 mg/L/degree GH = 1.08 degrees GH
Total: 2.86 + 1.08 = 3.94 degrees GH

Now Steve P. recommends adding CaCO3 until you get 4 degrees GH so this
should be adequate for most applications so my water should be pretty
good right out of the tap (except for Chlorine and temperature of
course).

How did I do?
Have I got the methodology right?