Odd Calcium Hardness Test


Well-known member
Jul 13, 2015
Clearwater, FL
I tried to test my pool water for calcium hardness today, but instead of getting a color change from red to blue, my testing solution precipitated red flakes into the solution and never turned blue. I tried repeating the tests three times, each with the same result, and for one test I used a newer R-0011L reagent. Any ideas what may be going on?


TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
NW Ohio
Is there any chance you have copper in your water? What you are describing seems to match what happens when there is copper present. Try following this step and see if that helps the situation:
NOTE: If the pool water contains known copper, add two drops of R-0012 PRIOR to adding R-0011L and continue. Count the two drops in your R-0012 total.