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Does anyone know of a reliable first-order or pseudo-first-order rate constant (or equivalent half-life time, from which I can get the rate constant) for the kinetic decay of aqueous chlorine in water (without photolysis or other reactions)? I have done a lot of web searching, read lots of...

A p.s.: I also appreciated the graphic you provided on the half-life curves at various levels of CyA. I had, however, already seen that when I first started "caring" about our pools. If you are running any chlorine into the pool at a relatively constant rate by any means (Trichlor, SWCG...

I appreciate your information on the CSI/LSI. Provides more detail on how it came about and how it applies. Thanks. After the county shut our pools down, and I then took over, we drained the pools entirely, cleaned them, refilled with fresh water and started over. We added granular Cyanuric...

I leave the measuring of grass heights and weed counting to the owners. Most of them could do with more outdoor exercise anyway. I just wish they would pick up after their dogs. We are currently running both pools at 50 ppm CyA +/- 2 ppm and 4 ppm FC, +/- 0.3 ppm through the day (it drifts, of...

Once again, Oops. Correction: "Now ask: What percentage (ratio) of Free Chlorine will be destroyed by the very same solar UV on December 21 (solstice) at noon? Ans: The percentage (ratio) of the unbound chlorine (HOCL/OCl-)." Should end: "Some percentage of the percentage (ratio) of the unbound...

Thank you AUSpool for your input. It clearly shows that you do understand the fundamental issue. Part of the following is an exercise in Logic using 2 excerpts from your recent posting with reference to Stanley R. Pickens: "the FC loss to UV is directly related to the unbound HOCl/OCl- . . ."...

To AUSpool: Yes, we are "constrained" in our allowable operating conditions. To be within Code in Pima County, AZ, operating a semi-public pool, you're required to be within 1 - 5 ppm FC, 0 - 100 ppm CYA, and 7 - 8 pH. And the Code requires twice-per day testing. Public pools are required to...

I totally agree. I'm not trying to achieve absolute accuracy in my own calculations. I don't know that anyone at all has documented, through lab tests, the degree to which chlorine bound in the chlorinated-cyanurate subspecies is degraded by UV, but I think that whatever value might be...

My thanks to AUSpool and mgftp for your comments. The .04 was erroneously entered by me, when I had intended .4. It's not "somewhere between". Ha Ha. About all I can say is that when theory doesn't match reality, it's time to revisit the theory. Particularly if you have any confidence that the...

Oops. That should have been .4 ppm FC loss, not .04 Transcription error.

In the ChemGeek's spreadsheet: Mark's test conditions are in the "Initial" column = Initial pool sample at 7.2 pH, 7.2 FC, 80 CYA. "Goal" column = Mark's 1st dilution sample at 7 pH, 3.6 FC, 40 CYA. Go to line 397 of the spreadsheet. The calculated "FC usage by sunlight (ppm/hr)" row. Mark's...

My apologies to any all who have followed my postings with resulting confusion and/or frustration with my ignorance, sometimes amplified by some of my muddled explanations. I'm sure there are many members with vastly more knowledge and ability than I in chemistry and mathematics for whom my...

It is proportional. FAC Molar concentration (Fraction) * Total Available Chlorine (TAC) PPM = FAC PPM. I'm not sure where you're trying to go with molar mass of Cl2 and FC PPM. But your math looks fine, to a point. To begin with, I think you'll find that 1 mole Cl2 in 10,000 U.S. gallons of...

I guess I didn't do a good enough job of presenting my information clearly enough in my initial posting of my "Observations". I did in fact validate Mark's test results and did in fact use the "Wahman calculator" - The EPA application I referred to and provided the link for. When I was...

Also, am I breaking this forum's protocols by using my real name? At 75 years old, I don't really care. But . . . I'd rather not be a thorn in everybody else's backside or make anybody uncomfortable.

Oh - And the doubling and quadrupling of the FAC molar concentration matched the doubling and quadrupling of the FC losses in the as985 test series.

When I first started estimating this I also thought that FAC ppm should be proportional to the FAC molar concentration. It is, but not in an intuitive way. The FAC molar fraction times FC ppm = FAC ppm. But after running mas985's test parameters in the EPA app and doing the math on the results...

No. I never believed that the FC/CYA ratio concept was "made up". I know that Lowry and Richard Falk both worked on developing the concept and that it appeared to be sound. However, following mas985's posting of his test there was a follow-on posting by Richard, which I can't locate again, in...

During the summer of 2021 we switched from using 3-inch Trichlor tablets in Pentair feeders to peristaltic pumps using 10% - 12.5% Sodium Hypochlorite (Bleach) hoping to reduce operating costs and to save water (periodically having to dump a lot of water due to constantly rising CYA). At peak...

In 2021 I converted our two HOA community swimming pools in Tucson, AZ (continuously in use throughout the year) from Trichlor erosion feeders to sodium hypochlorite using peristaltic pumps in an attempt to reduce overall costs and save water (otherwise periodically partially drained to contain...