Color questions for CH and TA

[TwinsPool]

Finished SLAMing and am starting normal maintenance. Some questions:

1. For the CH test, I see the color change from red to purple, and after a few more drops it seems less purple and more blue. Do I stop when the red changes to purple, or when the purple changes to what I guess is blue (although it seems to still have some purple in it)?

2. For the TA test, I see the green color turn first to pink, then after a few more drops it looks either very dark pink (according to my "other half") or actual red (according to me). Do I stop when the pink is evident or to the very dark pink/red point?

3. I see that the ideal range for CH on the laminated TF-100 instruction sheet for a masonry pool is 250-400 ppm. However, the ideal CH level for a plaster pool with liquid chlorine in the Recommended Levels article in Pool School is 350-550 ppm. For an elderly pool (vintage 1977), possibly replastered in 2018 by previous owner's pool guy, what actually is the ideal (and acceptible minimum and maximum) range for CH?

Thanks.

 

[Bperry]

Finished SLAMing and am starting normal maintenance. Some questions:

1. For the CH test, I see the color change from red to purple, and after a few more drops it seems less purple and more blue. Do I stop when the red changes to purple, or when the purple changes to what I guess is blue (although it seems to still have some purple in it)?

2. For the TA test, I see the green color turn first to pink, then after a few more drops it looks either very dark pink (according to my "other half") or actual red (according to me). Do I stop when the pink is evident or to the very dark pink/red point?

3. I see that the ideal range for CH on the laminated TF-100 instruction sheet for a masonry pool is 250-400 ppm. However, the ideal CH level for a plaster pool with liquid chlorine in the Recommended Levels article in Pool School is 350-550 ppm. For an elderly pool (vintage 1977), possibly replastered in 2018 by previous owner's pool guy, what actually is the ideal (and acceptible minimum and maximum) range for CH?

Thanks.

Both of those tests you keep adding drops until the color doesn’t change anymore, then subtract the last drop. That goofed me up for a while cause it’s kinda hard to judge what blue is correct.

The calcium is better adjusted using the CSI to track it and adjusted so the CSI is 0 or slightly negative. 0 to -0.3.

 

[mknauss]

Your CH test is doing what is called 'fading endpoint'.

See Calcium Hardness on how to test with that.

Test your fill water CH. I suspect it is 200 ppm plus. If so, do not add calcium to your pool. With evaporation, your CH will rise naturally (unless you are using softened water for make up water).

 

[TwinsPool]

Thank you both! This helps greatly!

I haven't tested my fill water yet, but, yes, we have hard water here. I am getting pool water CH tests of about 200-250 when I have recorded the "no-further-change" drop count (I recorded both early color change and no-further-change drops). I'm a bit surprised it isn't higher though, given that the water is very "old" and needs topping off every so often.

By the way, mknauss, I would like to thank you for what you wrote to another poster's question about cloudiness, which I was having a lot of trouble with during my recent SLAM. You mentioned that constant cloudiness while the pool is otherwise good with FC, etc, is likely a filter issue. I was beginning to think so also, so I inspected my DE grids closely and 3 of the 8 grid panels had significant holes in them! I replaced them and the next day I had clear water!