How does TFP account for free chlorine warnings on things?

[aquaN00b]

So I'm not a chemist, but I know the TFP FC/CYA chart was created and tweaked by those who are chemically inclined. It's been used well and proven to be tried and true. I'm a fan.

That said, if my CYA is 50 and I hold FC at 7 regularly, what credence am I to give all those product warnings I see about free chlorine levels? Some are even printed in bold and capital letters as if you are taking great risk in going over 4 ppm. The 3 examples I can think of off top of my head are:

Trichlor shock bags: Don't go over 4 ppm or risk bodily harm (pretty serious warning)

Dolphin Nautilus: not over 4 ppm I believe

Rheem propane heater: not over 5 ppm or risk equipment damage and warranty invalidation

 

[Donldson]

Those numbers assume a pool with zero CYA. Whether a company recognizes the effect CYA has on FC or not, they aren't going to print a table so just the most simple blanket warning they can put on a thing is what gets put on it.

 

[JH77]

Is there a safe-to-swim chart for CYA and FC ? I was just wondering the same thing.

 

[Donldson]

FC/CYA Levels
As long as you can see the bottom of the deep end it is safe to swim between the Minimum FC and SLAM FC (Shock FC) for your CYA level.

 

[JH77]

Thanks!