Wanted: Ward Labs reports for RO water (exclusively)

[Silver_Is_Money]

If you've ever had Ward Labs test your RO water, please post a copy of the report here. I'm trying to establish if there is any level of statistically valid correlation between TDS and bicarbonate/alkalinity for exclusively RO water.

My hope is that the following two simple and linear relationships can be generally well established:

1) ppm TDS = Factor * ppm Bicarbonate

2) ppm TDS = Factor * ppm alkalinity (as CaCO3)

Please do not attach Ward Labs reports for any water source other than reverse osmosis (RO).

Edit: Please also mention if your water goes straight to your RO unit, or if it first passes through a water softener, and then goes to your RO unit. This may reveal differences within any potential correlation.

 

[Silver_Is_Money]

As to my homes RO water, to date I have used only a KH test kit (liquid drops, not test strips) on it, to establish that its alkalinity is (via the KH method) 36 ppm. My RO water reads 45 TDS.

The same KH test kit indicates 436 ppm alkalinity for my straight well water. My well water reads 876 ppm TDS.

 

[bpinto]

Here are my RO (no water softener) results from Ward:

pH 7.2
Total Dissolved Solids (TDS) Est, ppm 42
Electrical Conductivity, mmho/cm 0.07
Cations / Anions, me/L 0.7 / 0.7

ppm

Sodium, Na 8
Potassium, K 1
Calcium, Ca 4
Magnesium, Mg 1
Total Hardness, CaCO3 14
Nitrate, NO3-N 0.5 (SAFE)
Sulfate, SO4-S < 1
Chloride, Cl 9
Carbonate, CO3 < 1.0
Bicarbonate, HCO3 19
Total Alkalinity, CaCO3 16

 

[Silver_Is_Money]

Thanks @bpinto

TDS = 8 +1 +4 + 1 + (other cations) + 0.5 + ~0 + 9 + 19/2 + (other anions)
TDS = 33 ppm plus some small unknown (via ion summation)

Not a very close TDS via ion summation check to their 42 TDS via (presumably) a meter reading.

For your RO water (and going with Ward Labs TDS):
----------------------------------------------------------
TDS = 2.21 * Bicarbonate
TDS = 2.63 * Alkalinity

This for no water softener pre-stage.

 

[Silver_Is_Money]

Since all TDS meters are factually merely conductivity meters with an internal multiplicative factor built in, and popular built in X factors typically range from 0.5 to 0.7, I wonder if Ward Labs valuation of TDS is derived (merely calculated) as 0.60 * conductivity scaled as uS/Cm (or MicroSiemens)?

Using this method I get: 70 uS/Cm conductivity * 0.60 = 42 TDS ppm (matching what they reported)

More of such data will either verify or disprove this presumption.

The uS/Cm to TDS factor for my personal TDS meter is 0.5, as mine is switchable between uS/Cm and TDS, and TDS is always half of uS/Cm on my meter.

 

[ajdelange]

As ppm TDS = Factor1 * ppm Bicarbonate = ppm TDS = Factor2 * ppm alkalinity (as CaCO3) ~ Factor2 * 50*ppm Bicarbonate/61 it's pretty clear that Factor1 = Factor2*50/61

Ward Labs TDS is merely scaled conductivity. I don't know what scale factor they use.