What to trust???

[TYarnell]

We opened our pool last weekend and as I have been testing the water I have noticed a huge discrepancy between what my test kit and what my test strips are saying when it comes my Calcium Hardness.
My test kit was brand new at the end of last summer, so I am inclined to believe that over the test strips, but am wondering if such a difference may be a result of the reagent for Calcium Hardness having gone bad? On the test strips the result was between 250 and 500 however, the result from my test kit is 65! I don’t want to add the 48lbs of calcium chloride if the test strip is right, but I don’t want to ignore what could be low calcium hardness if the test kit results are right.

I am using the La Motte ChlorQ 7 test kit and unexpired Leslie’s 7 in 1 chem strips.
Any advice would be greatly appreciated.

 

[ajw22]

Trust neither. The strips are guess strips and the ColorQ have issues with its CH testing.

Read about the ColorQ limitations in Pool Test Kits - Further Reading

I hate to tell you to get the TF-100 Test Kits but that is what you should have to use TFP recommendations. The numbers we use are based on repeatable testing using the TF-100 or Taylor K-2006C. Strips and the ColorQ give you different numbers and don't directly correlate with TFP recommendations.

 

[magiteck]

Hi TYarnell,

I wouldn't make any chemical changes based on either of those test results. Test strips we like to refer to as "guess strips" because they can be wildly inaccurate. I've read mixed findings on the ColorQ, but I wouldn't trust it enough to make a significant decision off of.

We recommend using a drop/titration based test kit, specifically either the Taylor K-2006C or the TFTestKits TF-100 (best value). See Test Kits Compared for more details/reading.

Hope this helps!
Jared