CYA Help

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Many users feel anything under shock level is safe, it's up to you. If you're worried about your suit you can wear an old one....

So the minimum would be the "min" for your CYA level on the chart, and the "max" would be shock.
 
No swimming tonight. Thunderstorms rolled through the area. :shock:

I shocked the pool tonight. Took a reading 45 min afterwords. Shut off the SWG. Took a FC reading with my limited test kit. I had to 50/50 the test because my current kit only records levels up to 10ppm. The FC level was easily 20+.

I'm leaving the pump on all night.

I will take another test in the morning and compare the results.

I plan to use the pool tomorrow. It's supposed to be a hot day.
 
I took a FC reading this morning as part 2 of the overnight test. The FC still appears to be 20+. Like I said, I can't be any more exact because of the accuracy of my current DPD test kit.

I'm not sure there is much more I can do other than wait for the new TFP CC kit before performing another overnight FC test...Turn SWG on...Test FC twice a day to ensure it is at or near target level. Sound ok?
 
If the water is clear and sparkly, I would turn off the SWG until the FC level comes down a bit. If there is still any chance that there is algae I would leave the SWG on and let the FC level come down more slowly.
 
As shown in the Chlorine/CYA Chart the minimum Free Chlorine (FC) level for an SWG pool with 75 (call it 80) ppm Cyanuric Acid (CYA) is 4 ppm. This will prevent algae growth and be more than enough to kill pathogens reasonably quickly.

As for how high a chlorine level is still safe to swim in, that's partly a matter of personal choice. So long as you don't drink the water (in quantity), you could swim even at shock level because technically the shock level in the chlorine/CYA chart corresponds to roughly 0.3 ppm FC with no CYA which is far lower than found in most indoor pools (that don't have any CYA in the water). Of course, if the water is cloudy, you shouldn't swim since it's unsafe if you cannot see someone at the bottom who may be drowning.

Richard
 
I just performed my second overnight FC test (with my new TFP FAS-DPD mix - which I love). The FC held overnight at 11.5ppm. CC level 0

It safe to assume the water is clean. The only alarming issue I notice is I shocked the pool to 21+/- ppm on Friday night. I had the SWG on 30% Saturday, pool got sun a majority of the day. I'm surprise how quickly level dropped from 21 to 11.5ppm in one day with a CYA of 75. The family used the pool twice for a total of 1-2 hrs. Does this sound normal?

I'm going to turn SWG on at 50% today and test FC periodically throughout the day to see where the levels go. I will adjust SWG output accordingly tonight after sundown. My current filter time is 9 hrs (8am to 5pm)
 
When adjusting the SWG percentage, you should focus on the FC level in the early evening. You need to test the water at a consistent time of day to get repeatable results. Early evening is the best time to do that, because that is usually when FC is lowest.

Testing throughout the day isn't a problem, and if your percentage setting is way off, it can be help full. But for reliable fine tuning you want to focus on early evening tests.
 
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