Calcium hardness

[EndlessSummerAZ]

I keep running into a fading endpoint with the calcium hardness test. I’ve tried both methods the site suggests of adding the R-0012 drops first and the distilled water method. Both seem to still produce a purple color before it turns blue.

The fact that I’m in Phoenix leaves me no doubt my calcium is high but I’d like to be able to figure out this test. Any suggestions? Do I just keep reducing with distilled water?

 

[Obecalp86]

I’ve had the same issue - also in Phoenix. There must be something in the water here.

Mine also turns purple, then blue, and I record my calcium hardness when it turns blue. I think you’re fine.

If I use distilled water in place of half of the pool water sample, then I get the proper blue endpoint, but if I let it sit a few minutes then it turns purple.

Edit: adding R-0012 first, as has been suggested by many, does absolutely nothing for me.

 

[JoyfulNoise]

I keep running into a fading endpoint with the calcium hardness test. I’ve tried both methods the site suggests of adding the R-0012 drops first and the distilled water method. Both seem to still produce a purple color before it turns blue.

The fact that I’m in Phoenix leaves me no doubt my calcium is high but I’d like to be able to figure out this test. Any suggestions? Do I just keep reducing with distilled water?

Your logs show your CH is 1200ppm. I’m assuming that’s an older value and it’s probably higher. The Taylor test is only really good up to 800ppm and that’s pushing the limit.

Use 1 part pool water added to 3 parts distilled water (3:1 dilution) then test using the fading endpoint protocol. Multiple your final result by 4. For fading endpoint, add the R-0010 FIRST and then add a few drops of R-0012, then indicator, then titrate. Add up all the drops of R-0012 for your final count.

 

[mknauss]

There is iron in Colorado River water. That builds in your pool with evaporation.