Calcium and Carbonates Confusion

[tudou]

I have several figures for calcium and (bi)carbonates and was hoping I could get some advice on which are the most suitable to use.

Firstly, I have some values quoted from Scottish Water who stopped recording these figures in 2005:

Ca: 17.2 mg/L
Ca Expressed as CaCO3: 42.9 mg/L

I also have an API GH & KH test kit which gives the following results:

KH: 35.8 ppm
GH: 71.2 ppm

Plugging the KH and GH into Bru n' Water, that gives:

Ca: 28.6 mg/L
HCO3 (Bicarbonate): 43.5 mg/L

Other parameters are:

Sodium: 5.75 mg/L
Sulphate: 15.775 mg/L
Chloride: 11.778 mg/L
Magnesium: 1.6 mg/L
Iron: 0.0228 mg/L
Nitrate: 2.5 mg/L
Nitrite: 0.002 mg/L
Fluoride: 0.02 mg/L
pH: 7.4