Copy/pasting comment made to me after I posted about my son getting sick from a Lunchable.
Just adding to the pool angle.....could sorely use correcting where applicable from our members more knowledgeable in chemistry as I'm working from an ancient memory.
chloroamines (sp) are poor disinfectants against viruses and the more potent disinfectant agent formed by sodium hypochlorite is hypochlorous acid. Noroviruses are transmitted readily through a variety of pathways including stool. It's my understanding pools are infamous for its transmision and that Norovirus is more difficult to disinfect for than Hepatitis. It's my understanding the recommendation is that persons with gastroenteritis or diarrhea not enter swimming pools until two weeks after infection because of this and it's overall infectiousness. (Maybe I'm wrong)
I'm also of the understanding that the more effective disinfecting agent in chlorine is hypochlorus acid which is readily lost over time when chlorine becomes liquid (liquid chlorine) and that household bleach contains less of this form than pool chlorine. Call me a sucker and I could be wrong.
Chem whizzes, I could stand some correcting, this is all very foggy for me.
So I might as head down the foggy path further and say that "CYA", I understand to be a stabilizer of sorts for chlorine in sunlight, but....is retained over time in the water to the point it can significantly renders chlorine ineffective (even if a pool smells strongly like chlorine) Pool sanitization should not be based on whether a pool smells like chlorine.
Anyway, this is all so foggy for me that one way we avoid the pitfalls is to drain nearly all the water out of the pool at the beginning of each season and start fresh. No "old chlorine/pool chemical" byproducts that interfere with santization or stabilization of the water.
No advice, just what I barely remember. You'll probably never know what caused it, but at this point, since your son has been back in the pool so soon after the initial illness, you should make sure what would kill any "what-if's".
Okay, I started a thread at a site I visit about Lunchables and my son got sick from them, the Lunchables. She went on this diatribe about how I sanitize my pool and wrote the above. Well, I explained to her the BBB method I'm using and she thinks he did indeed get sick from swimming in my pool because bleach is ineffective.
I beg to differ though cuz my kids have never gotten sick from using it other than an ear ache because my son got water in his ear.... he's a chronic sufferer but wears plugs.
What do you guys think?