Hi, I have done several tests on my pool for calcium hardness but I am having trouble pinpointing the level. I use a Taylor test kit.
The first few times, after adding the calcium hardness liquid, I would get more of a magenta color than a true red. Adding the hardness reagent would turn the solution to a bluish-purple instead of a definitive blue. There would be a range of a several drops to get from where it looked plain purple to start getting a bluish hue.
Finally, I noticed something in the instructions about metal ion interference and that adding some hardness reagent before would bind those ions. I tried this by adding 6 drops of hardness reagent to the 25 ml sample but still got the magenta and bluish purple. However, after getting to 24 drops and not seeing anymore change after swirling, I set it down and to do something else and came back in 2 or 3 minutes. The solution was now totally blue.
The instructions don't say anything about a very slow color change. How fast is it supposed to happen? Should one drop take it from red to blue? Or is it supposed to be a gradual color change with several drops needed after going from red/magenta to a definite blue?
This is a 6 year old pool but I am the new owner since December so I don't know what has been put in it.
During these tests the other levels were as follows:
FC 1 - 5 ppm
pH 7.5 - 7.7
TA 140 - 150 ppm
CYA 42 - 46