Having a hard time with Calcium Hardness test on Taylor K-2006

[crystallake]

Hello all,

I am having a heck of a time getting results I can rely on when testing for calcium hardness. I follow all the steps, but sample never really changes colors from red to blue as indicated on the instructions. It does turn a kind of purple, which is what I have been relying on, but then a new problem arose. The same would change purple at around 45 drops...s0 450ppm calcium hardness. Easy enough, right? But then I took water to Leslies to run a test and it came back at 300ppm of calcium hardness. I am a bit at my wit's end and would like any suggestions here. The calcium reading has a significant impact in my CSI and LSI calcs so I would like to have a relatively good idea of where my readings should be. Any help is appreciated.

15,600 gallon plaster pool with SWG.

 

[mknauss]

Use a 10 ml sample. Each drop of R0012 to blue is 25 ppm CH. A SpeedStir really helps.

I suggest you follow the metals interference process described in Calcium Hardness

Another option is to cut the pool water 1:1 with Distilled Water. Then use that mix for the 10 ml sample. Do the test and double the results.

 

[flynwill]

I've also had similar issues with the CH test. The procedure I now use is a variation on mknauss's suggestion: Fill the sample vial to the 10 ml line with pool water, then add 15 ml of distilled water (bringing the level to the 25 ml line). Now follow the directions for the 25 ml version of the test (20 drops R-0010, 5 drops R-0011). But multiply the number of drops of R-0012 by 25ppm. Also slow down when you get close to the expected CH as it may take a second or two for the color change to develop.

 

[crystallake]

Use a 10 ml sample. Each drop of R0012 to blue is 25 ppm CH. A SpeedStir really helps.

I suggest you follow the metals interference process described in Calcium Hardness

Another option is to cut the pool water 1:1 with Distilled Water. Then use that mix for the 10 ml sample. Do the test and double the results.

Thank you for this. I do have a SpeedStir, which definitely helps with things.

I tried the metals interference guidance and I still experienced the fading endpoint. I had a bottle of distilled water on hand (thankfully) and that worked like a charm; however, I turned blue at 10 drops which puts me back at the 480-500 results that I had been getting previously. Would you suggest I trust the Taylor kit over the 305 result that I got at Leslie's?

Thank you for your help with this.

 

[mknauss]

Would you suggest I trust the Taylor kit

Absolutely.

 

[crystallake]

I've also had similar issues with the CH test. The procedure I now use is a variation on mknauss's suggestion: Fill the sample vial to the 10 ml line with pool water, then add 15 ml of distilled water (bringing the level to the 25 ml line). Now follow the directions for the 25 ml version of the test (20 drops R-0010, 5 drops R-0011). But multiply the number of drops of R-0012 by 25ppm. Also slow down when you get close to the expected CH as it may take a second or two for the color change to develop.

This is extremely helpful. Thank you. Between these two suggestions I think I am dialed in. Now it's just the question of the discrepancy with Leslie's test result, but I have a feeling I know where that answer is going to fall.

 

[crystallake]

Absolutely.

Perfect! My CH at 480 was easier for me to maintain proper CSI and LSI levels given my pool's tendency for a higher pH so this is comforting to know my water was in good condition all this time. Thank you again!

 

[flynwill]

The other thing I have seen is that sometimes the drops of R-0012 are smaller than they should be which will cause a high reading. There is a specific caution about this in the TA instructions, but I have found it can happen with any of the drop tests. What I do is press the tip of the reagent bottle against a clean paper towel, and let a drop of reagent onto the paper to wet the entire surface of the dropper tip.
That said I would trust your own testing over the pool store.

 

[mgtfp]

It also helps to squeeze the bottle a bit before inverting it. Like that you create a slight underpressure that balances the gravity push, particularly in relatively full C-sized bottles, and you have better control how fast and when the drops form.