CYA = Zero

[chem geek]

EricH,

It's not just that a zero CYA won't protect the chlorine from sunlight, but that the disinfecting chlorine level will be too high and will be more corrosive to metal, swimsuits, skin, etc. Indoor pools without CYA are like that, though they usually try to run at lower FC (2 ppm or so).

In this post you also mention no CYA even when using Trichlor which doesn't make sense. If you had no CYA in your water, then your FC would drop in half in about 30 minutes in direct noontime sunlight and it seems that this is not happening for you even with the limited amount of sun exposure. I suspect you do have CYA and for some reason it is not getting measured.

Richard

[EricH]

Interesting information, thanks. Didn't realize CYA helped with the corrosiveness of the water.

The pool is usually covered when the sun is out, but I do occasionally have to fight to keep FC up, so who knows.

To clarify though, even if my tests aren't catching it, I shouldn't need to add raw CYA if I'm using trichlor tabs in an auto-chlorinator (which runs all night.) The CYA must be getting in there, and my understanding is that once it's in there, it doesn't go away until you dilute the water.

Love the forum!

E