OK, I'm gonna take this one. But, I've got to be careful, because my dislike for Kent Williams extends beyond what is completely reasonable.
(Reading over this, I realize that my dislike of Kent still shows through. I tried to prevent that, but I'm not going to rewrite it again. Just realize that -- although I think I got my facts right, I dislike the man, and couldn't keep that out of my post.)
First: A full answer to the question of cyanuric acid (stabilizer) and chlorine requires getting into the whole issue of the chemical relationships that exist among the various. Richard (Chem Geek) has gone further than anyone else . . . and MUCH further than Kent Williams . . . in understanding and explaining analytically what's going on. But, that answer is very complex, and while much of Richard's analysis is consistent with the practical conclusions I reached when I published my "Best Guess" chart, and consistent with the experiences of (now) thousands of pool owners, it still has never been verified experimentally in a formal, repeatable sort of way.
If that's REALLY the sort of discussion you're interested, Richard can (and probably will) take it up with you, but we first need to move this thread into the China Shop.
Second: Kent is not a disinterested pool observer with nothing to sell, and the PPOA is not an 'independent' association. Rather, he is very aggressively -- but somewhat deceptively in my opinion -- selling his consulting services and the PPOA, which he entirely owns and controls. This is the issue that lies behind my dislike of Kent: I was deceived by him, and thought that the PPOA was independent, and that he was just its representative, rather than its owner and proprietor. He didn't even attempt to correct this misunderstanding, even in the personal contact we had years ago.
Third: The "Benefactor or Bomb" chart is old data, more than 10 years old. And though he knows of the work done here, and at Trouble Free Pools, and by Richard, since then, he hasn't changed anything to reflect that new information. There are reasons why he wouldn't want to do so that have to do with his past history with Strantrol and commercial pools, but again, that's China Shop stuff.
Richard has responded to virtually the same question you asked, and responded rather more generously than I would, suggesting that Kent's information applies more to commercial pools than residential ones. I'm not going to do that: Richard knows more about the chemical relationships among chlorinated cyanurates in pools than anyone I know . . . but I know a LOT more about operating large commercial pools than either Richard or Kent. The "Best Guess" guidelines to chlorination apply just as well to large commercial pools, as they do to residential pools. In fact, because of the way apartment and hotel pools tend to be operated, they would be MUCH safer if they were operated with high CYA / high chlorine per the Best Guess chart, then if they were operated per Kent's recommendations.
Finally: Kent, as an old Strantrol employee, is very pro-controller in his thinking. The problem is that using ORP (or "redox) measurements to control chlorine levels on outdoor pools is very problematic. The reasons are complex and technical. The presence of CYA makes these problems much more difficult to resolve. Strantrol -- years ago -- adopted the tactic of slamming CYA as a sales and product promotion tool, since their products don't work well on stabilized pools. Kent should disclose his connection to all this, but doesn't. The fact that he doesn't makes me pretty skeptical about the reliability of his "data".
Bottom line: if you want to run your pool well, operate it according to the Best Guess Chart, or according to Richard's more complex version at TFP. If you want to dig into the complexities of chlorinated cyanurate chemical equilibrium levels, and the relationship of these equilibrium levels to ORP or redox levels, to oxidation rates, and to sanitation, that's fine too. But we need to move this thread to the China Shop first.
Best wishes,
Ben / PoolDoc
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