Testing Calcium Hardness

[creechy]

I use a Taylor Test Kit for checking my calcium hardness. When adding the R-0012 it turns from red to what appears as purple before going to a blue color. Is that normal? Do I stop counting when it turns purple or wait until it turns blue?

Thanks for your help!

 

[jblizzle]

On all the tests, you add drops until the last one results in no further color change and do not count that drop. A nice sky blue is the usual end point for the CH test.

 

[JasonLion]

The sample may turn purple during the test, or go to blue for a moment and then turn back to red/pink. This is called a "fading endpoint" and is caused by interference from metal ions. A fading endpoint tends to cause the test to read higher than actual. Sometimes you can simply swirl the sample for longer and the purple will change back to either red or blue.

More generally, when this happens, do the test again, but this time add five drops of R-0012 before adding any R-0010 or R-0011L. Remember to count the initial five drops in the total. In extreme cases, a fading endpoint may occur even when adding five drops of R-0012 at the start. If that happens, mix pool water with an equal quantity of distilled water, test that, and then multiply the result by two.

 

[creechy]

Thank you for the help!! I will try the 5 drops of R-0012 and then watch for the final drop when it no longer changes.