In recent months I've had ever-increasing levels of TDS and Salt. That is, according to the Aqua Chek Salt strips and TDS strips I've been using. My doubts prompted me to repurchase both in August, thinking that the strips may have been old (although I'm fairly scrupulous in my care of them.) When I conducted testing with the new strips I got... exactly the same results.
TDS > 5000 and Salt ranging from 3660 to 3970. My PS-8 Aqua Logic controller reports salt consistently at 2900-3000 ppm. I believe that the salt cell measures on the basis of conductivity and, per several comments I've seen, reports salt ppm based on its finding minus some variable to account for other dissolved solids. In an effort to resolve the apparent discrepancy between the strips and the SWG, I recently acquired drop tests for TDS and sodium chloride, repeating the tests with the Taylor kits and the newer Aqua Chek test strips. For a comparative analysis, please see the attached Excel spreadsheet.
My tentative conclusions:
- Observation 1: Salt cell reports ~2900, sodium chloride drop test reports 3000, Aqua Chek strips 3970
Observation 2: TDS drop test reports 2400 as CaCO3 but Aqua Chek shows TDS off the chart: 5000+
Hypothesis: Aqua Chek salt strips overreport sodium chloride; the Pro II TDS strips may include salt in total
I'd love to hear what others have to say about these findings. Thanks!