So how come there aren't a LOT of sick people?

[waterbear]

Been following this thread and need to add a few comments. The following gets somewhat technical so you have been warned!
1. When the article on CYA is talking about automatic delivery of chlorine it is NOT talking about a SWG. It is talking about using a peristataltic pump and an ORP controller to automate the addition of liquid chlorine to a pool to maintain a certain redox potential...apples and oranges, not the same thing at all.
2. the author of this article was/is connected with a company that manufactures ORP controllers for pool and CYA messes up ORP readings. ORP controllers work best when there is no CYA present by constantly dosing the water with chlorine as it is demanded by use.
3. Let's examine a quote from the article (with empahsis added by me):
"An ORP level in water of 650
mV is the most widely accepted minimum for qualitative
results, worldwide.
650 mV of ORP can be achieved with a variety of
chemical compounds, conditions, and influences. It is “qualitative”.
650 mV is the same working value whether it takes only
.1 ppm “free” chlorine at pH 7.2 with no CYA to get there or 3
ppm at pH 8 in the presence of 30 ppm CYA to make it. In the
second of these two extreme examples it takes 30 times more
chlorine to achieve the same results. All it took was a pH elevation
and the addition of cyanuric acid."

when sodium hypochlorite is added to water it dissociates into hypochlorous acid and hypochlorite ions. Hypochlorous acid is what has the oxidizing ability...hypochlorite ions do not. The ratio of hypochlorous acid to hypochlorite ions is pH dependant. At a pH of 7.2 over 75% of the chlorine is in the form of hypochlorous acid so the oxidative ability is very high!
At a pH of 8 less than 20% of the chlorine is in the form of hypochlorous acid. It is a given that the addtion of cya will have an effect on lowering the oxidative ability somewhat since chloroisocyanurates are less potent oxidizers than hypochlorous acid. However I submit that it is the change in pH that has the most impact on this example. The differential in oxidative ablilty with just a change in pH is over 55% for a given level of residual chlorine! IF my math is correct it would take over 1.8 ppm FC at pH 8 with NO CYA to achieve the same results as .1 ppm at pH of 7.2. The addition of 30 ppm CYA only affected the results by slightly over 1 ppm (about 35% more needed) while the change in pH needed about 170% more chlorine for the same oxidative ability when no CYA is present!
Which is the parameter that has the greatest impact here....pH or CYA? I submit it is the pH!
4. The author states at the end of the artice
"This writer has, by the way, used cyanuric acid successfully
and with benefit in his own pool for years."
This certainly sounds like an endorsement for using CYA to me!