Jandy SWCG's "optimal" water conditions: why raise CYA?

[waterbear]

To answers your first question:

Higher CYA levels translate into lower cell on time which translates into less hydrogen gas generation in the cell which translates into less aeration of the water which translates into less outgassing of CO2 which is the primary cause of pH rise in salt pools (barring new curing plaster).
NOT dropping the pH below 7.6 and lowering it back down to 7.6 and not lowers (and not letting it rise above 7.8-7.9 and always keeping it below 8.0) slows pH rise (the lower you put pH the faster it rises) and helps minimize the possiblity of scaling condtitons.

Running the TA low (70 ppm seems to be optimal) translates into less carbonation n the water which translates into less outgassing of CO2 which translates into better pH stablility and slower pH rise.



For the second:
It's not warm water, it's sun exposure. If the pool temp is that high then it is assumed the pool is getting a lot of sun and higher CYA is beneficial in ANY pool, salt or not. BEST place for CYA is at the manufacturers recommended maximum so get yours up to about 80-90 ppm givin that you are in Florida (even in my N. Fl pool the temps stay in the high 80's during the summer and the pool is in a screen room!
Today my pool is at 89 degrees and it's before noon!)

for the third:
Optimum level for FC is about 5% of the CYA level, generally 4-5 ppm. This way you do not need to worry about algae outbreaks or the need to superchlorinate at all!

for #4:
It depends on a lot of factors. First, the type of metal involved (titanium and ferro cupric alloys in heat exchangers are more corrosion resistant). It depends on other ions in the water (sulfates from dry acid and non chlorine shock for example). It depends on salt level (depending on manufacturer SWCGs operate anywhere from less than 3000 ppm to sea water salt levels with most falling somewhere in the 3000-6000 ppm salt range. Even at 6000 ppm the water is not considered particularly corrosive). It depends on whether there is a sacrificial anode in the pool. It depends on pH (low pH is probably one of the biggest factors in predicting metal corrosion.)

for #5:
Shocking with the boost or superchlorinate function:
1) shortens cell life
2) causes FC level to slowly rise over the time period the boost function is on and this is not the most efficient way to superchlorinate and can actually cause some undesirable oxidation byproducts to form.
3) it is slower since you need to wait for the cell to generate enough chlorine to reach the desired level which can take as long as 24 hours just to reach shock level and then you need to wait for it to drop down after, which can take up a day or two longer.

Shocking with chlorine or bleach:
1) does not shorten cell life
2) brings the FC level up to your target shock value immediately and is therefore much more effective chemically in oxidizing and killing algae
3) the entire process is much faster since you do not have to wait for FC level to rise, it is instantaneous. You just need to wait for it to drop.