Have you been brushing ? If you have a light check the niche. Algae will sometimes hide out in it. Check ladder if you have one. Any where algae cold hide out.
I brush every day. Light was out for 3 days, clean behind it. I put the light back in place last night. Ladder is formed into the plaster in the deep end, no metal ladder in the water. Visually, there is literally no place for the algae to be hiding. It could be in the plumbing, but what are the chances. I had the pipes open the replumb the filter and add the swg, insides of the pipes were clean.
I did read this on Taylor's website:
" When monopersulfate is present in the sample, it reacts with DPD #3 in the total chlorine test, producing a dark pink/red color characteristic of a high total chlorine reading. However, monopersulfate will not react with the DPD #1 and #2 reagents used to measure free chlorine. Therefore, the combined chlorine level obtained doing the calculation above is artificially high.
In an FAS-DPD drop-count titration, you add DPD indicator powder to the water sample and it will turn pink if free chlorine is present. Next you add FAS-DPD titrating reagent drop by drop until the sample changes from pink to colorless. You then multiply the number of drops added by an equivalence factor (stated in the test instructions) to get the free chlorine reading. Finally, you add DPD #3 reagent to the treated sample, which will turn pink if combined chlorine is present. Once again, you titrate until the sample turns colorless and multiply the drop count by the given equivalence factor to get the combined chlorine reading. If monopersulfate is present in the sample it will react with DPD #3, artificially increasing the combined chlorine reading.
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I bought the house a little over a year ago, and do not know what the previous pool guy was using to take care of the pool. Although, like I said, I have never had a problem with CC for the past year I have been maintaining the pool.
