CC clorine present after shocking...

[gtnos]

first off, i know everything is fine, water is crystal clear and all tests come up right on the money. we left out friday at noon to the lake. before we left i dumped 1 1/2 gallons of 8% into pool to bring it to shock level (24 ppm for 6423 gallons) i covered it with crappy intex cover and we took off.

fast forward today, we got home at 200pm, it had been raining today (thank goodness, we needed it) and the crappy intex cover had sunken into pool (good thing i already ordered a better winter cover)

pool was crystal clear, only needed a little vacuuming and skimming.

FC tested perfect at 7.5, so my chlorine loss calculations due to full sun on pool i did before leaving were spot on...

interesting though.... CC was slightly pink. it is less that 5ppm, but normally it is 0pmm every day. i found this interesting with such a high dose of chlorine and no usage of the pool for 3 days. :?

thoughts?

 

[techguy]

The cover likely trapped the little CC you do have. The sun will drive it off if you leave the cover off while its in sun.

 

[chem geek]

Also, depending on exactly where you end up with the last FC drop in the FAS-DPD test, you can either see a slight pink or clear for the CC part of the test. The FC can overshoot into the CC since these two tests overlap. So getting rid of that last bit of pink in the FC part of the test can have extra FAS reagent in the water to use up CC when you add the R-0003 reagent for the CC part of the test. If by chance your last FAS drop in the FC part of the test just barely turned it to clear so there was little FAS leftover, then you'd see a slight pink in the CC part of the test if there was even just a little CC.

In short, don't worry about it. If you are really curious as to the amount, then use a 25 ml sample size which as a resolution of 0.2 ppm. I suspect you've got less than 0.2 ppm CC and that's absolutely nothing to worry about.

 

[gtnos]

The cover likely trapped the little CC you do have. The sun will drive it off if you leave the cover off while its in sun.

that makes sense. thanks.

Also, depending on exactly where you end up with the last FC drop in the FAS-DPD test, you can either see a slight pink or clear for the CC part of the test. The FC can overshoot into the CC since these two tests overlap. So getting rid of that last bit of pink in the FC part of the test can have extra FAS reagent in the water to use up CC when you add the R-0003 reagent for the CC part of the test. If by chance your last FAS drop in the FC part of the test just barely turned it to clear so there was little FAS leftover, then you'd see a slight pink in the CC part of the test if there was even just a little CC.

In short, don't worry about it. If you are really curious as to the amount, then use a 25 ml sample size which as a resolution of 0.2 ppm. I suspect you've got less than 0.2 ppm CC and that's absolutely nothing to worry about.

chem geek: WOW!!! although it took me 3 times reading that answer to fully understand it.... :lol: that was a GREAT answer!!! i wondered how the FC test affected the CC test since they overlap. thanks for the tip on using the 25 ml sample to test for amounts smaller than 5ppm.... although im rarely THAT curious, but its nice to know anyway. thanks!