This is the third time I've opened this pool, which we acquired with our new home just over two years ago. I closed the pool last December, which is a very late closing here in Idaho, because I wanted to give my late-season Jack's Magic #2 treatment the longest time possible to work on copper stains that I believe were the result of the previous owner using trichlor with copper.
As expected, the sulfamic acid in the #2 treatment resulted in nearly all the chlorine reporting as CC. Even after 12 weeks (most of it above the recommended 60 degree water temperature), my pool still read nearly all CC (last December). Now I read about 2 ppm FC and 14 ppm CC (I'm SLAMing). In reality, the FAS DPD test doesn't work well at all, because the CC bound from the sulfamic acid takes a fair amount of time to react. The same is true of OTO. Jack's recommends just using OTO and I think OTO works just as well as FAS DPD, due to the unknowns about sulfamic binding of chlorine and the uncertainties of any test in a sulfamic acid treatment chemistry.
The first two seasons that I opened the pool revealed CYA (and, naturally, TC) to have fallen to zero but the water was clear. Not so this year. The CYA reading was nearly where it was when I closed (still a bit over 30 ppm) and the pool was green. This is day three of the SLAM. As best I could tell using both FAS DPD and OTO (diluted pool water 1:3 with fresh water) the pool did not discernibly consume chlorine last night. The water is clearing and the cloud is mostly white.
I know TFP experts advise not to use OTO with a diluted sample to establish and check SLAM chlorine levels, but there's really no point in doing FAS DPD because the clear to pink reaction time is so prolonged (not the normal re-occurance of pink due to a prolonged test time) OTO is cheap and easy but it takes about an hour to fully detect the sulfamic bound chlorine. In fact, there's no color at all for several minutes. I just set the comparator aside for an hour and then take the reading.
It was the same during the Jack's treatment and there's little technically known about how chlorine functions under the stain treatment or even what chlorine concentrations are needed during a SLAM. The bottom line is my pool is clearing normally.
During the #2 treatment, I noticed that chlorine demand was a bit higher than normal too--especially given the colder months. I don't know if it was because the chlorine was becoming bound in a sulfamic acid reaction or perhaps it was due to an "infection" in the pool.
Before I closed the pool, I used baking soda to balance the pool, as recommended by Jacks but I did not SLAM, faring stain precipitation. I didn't SLAM the the previous closing either but rather used Polyquat 60.
So the bottom line is a pool may behave a bit differently after Jacks's #2. From reports and my experience, it takes many months to "get it back" and probably a lot of chlorine too! In the meantime, the diagnostic aid of a FAS DPD FC vs. CC is obliterated--you'll just have to live with a somewhat uncertain TC/CC reading and the chlorine tests don't behave as usual.
As expected, the sulfamic acid in the #2 treatment resulted in nearly all the chlorine reporting as CC. Even after 12 weeks (most of it above the recommended 60 degree water temperature), my pool still read nearly all CC (last December). Now I read about 2 ppm FC and 14 ppm CC (I'm SLAMing). In reality, the FAS DPD test doesn't work well at all, because the CC bound from the sulfamic acid takes a fair amount of time to react. The same is true of OTO. Jack's recommends just using OTO and I think OTO works just as well as FAS DPD, due to the unknowns about sulfamic binding of chlorine and the uncertainties of any test in a sulfamic acid treatment chemistry.
The first two seasons that I opened the pool revealed CYA (and, naturally, TC) to have fallen to zero but the water was clear. Not so this year. The CYA reading was nearly where it was when I closed (still a bit over 30 ppm) and the pool was green. This is day three of the SLAM. As best I could tell using both FAS DPD and OTO (diluted pool water 1:3 with fresh water) the pool did not discernibly consume chlorine last night. The water is clearing and the cloud is mostly white.
I know TFP experts advise not to use OTO with a diluted sample to establish and check SLAM chlorine levels, but there's really no point in doing FAS DPD because the clear to pink reaction time is so prolonged (not the normal re-occurance of pink due to a prolonged test time) OTO is cheap and easy but it takes about an hour to fully detect the sulfamic bound chlorine. In fact, there's no color at all for several minutes. I just set the comparator aside for an hour and then take the reading.
It was the same during the Jack's treatment and there's little technically known about how chlorine functions under the stain treatment or even what chlorine concentrations are needed during a SLAM. The bottom line is my pool is clearing normally.
During the #2 treatment, I noticed that chlorine demand was a bit higher than normal too--especially given the colder months. I don't know if it was because the chlorine was becoming bound in a sulfamic acid reaction or perhaps it was due to an "infection" in the pool.
Before I closed the pool, I used baking soda to balance the pool, as recommended by Jacks but I did not SLAM, faring stain precipitation. I didn't SLAM the the previous closing either but rather used Polyquat 60.
So the bottom line is a pool may behave a bit differently after Jacks's #2. From reports and my experience, it takes many months to "get it back" and probably a lot of chlorine too! In the meantime, the diagnostic aid of a FAS DPD FC vs. CC is obliterated--you'll just have to live with a somewhat uncertain TC/CC reading and the chlorine tests don't behave as usual.