Not sure what y% is--tho x% is obviously 50% in this example.

I think the reason that the disinfection at higher temps (when the organisms are also reproducing the most) works better can be explained simply. The organisms' metabolism is faster at warmer temps--that's why the reproduction rate increases. That means they are also metabolizing the POISON faster too--after all, that's what our FC is, poisoning the organics--which is why the it's more effective.

But the idea that there's giardia and crypto in the pool, along with e-coli, makes my skin crawl--and pour in another gallon of bleach!