Ward Labs results came in today. I sent two samples: 1) for Brewer's test and 2) for Household test. Based on the results listed, I think the samples got crossed. I ran the same water supply through your generic 10" carbon block filter one of the tests. Results below -
Sample 1 Sample 2
pH 6.6 8.6
Total Dissolved Solids 65 62
Electrical Conductivity 0.11 0.10
Cations/Anions 1.0 / 0.9 1.0 / 1.0
Sodium, Na 10 10
Potassium, K 1 1
Calcium, Ca 10 10
Magnesium, Mg < 1 < 1
Total Hardness, CaCO3 29 29
Nitrate, NO3-N 0.3 < 0.1
Sulfate, SO4-S 5 3
Chloride, Cl 7 5
Carbonate, CO3 < 1.0 < 1.0
Bicarbonate, HCO3 19 36
Total Alkalinity, CaCO3 16 31
Total Phosphorus, P 0.02
Flouride, F 0.3
Total Iron, Fe 0.03 0.11
I was a little surprised to see the bicarbonate, alkalinity, and pH go up so much with the filter in place. This was an old filter, one used often. Maybe it hasn't been stored so great.
Source is public water supply, Anne Arundel County, MD - Odenton/Crofton supply.