Trichlor = How much CYA?

I know I've seen it here before, but I could not find it--- so how much CYA does Trichlor tablets add to pool?

Thanks

For every 10 ppm FC added by trichlor you also add 6 ppm CYA.

And, on a similar note in case someone is interested, with dichlor, for every 10ppm FC added, it adds 9ppm of CYA.

This doesn't make sense to me. I moved to a house where previous owner exclusively used tablets for many years. Sure, CYA ended up being somewhere between 240-300 but shouldn't it have gone up to much higher number?

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After the drain and refill, CYA is now somewhere between 70 and 80.
Hopefully this will make it easier for me to keep algaes away. I plan to keep chlorine level between 5 and 10.

Quote:

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Originally Posted by han78216

This doesn't make sense to me. I moved to a house where previous owner exclusively used tablets for many years. Sure, CYA ended up being somewhere between 240-300 but shouldn't it have gone up to much higher number?

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Not necessarily. If he had a sand filter, backwashing and other water loss would limit the upper concentration. But . . . . test results showing 240 ppm CYA are highly suspect. Unless he was VERY careful and did VERY good dilutions, his 240 ppm might have been 600 ppm!