FC & CYA - I don't understand...

[bluesixer]

I'm guessing the answer to this question is obvious and I sound like an idiot for asking, but here goes...

If CYA (aka conditioner) protects chlorine from being evaporated by sunlight, why do target and shock FC levels go up as CYA goes up?

It seems like the more chlorine protecting CYA there is in the water, the less chlorine should be required - but the chlorine/CYA chart says the opposite.

What about this am I missing?

 

[Catanzaro]

For starters, there are no dumb questions here on the Forum. Welcome to TFP!

Below are links on the relationship between CYA and FC:

Chlorine / Cyanuric Acid (CYA) Relationship - Pool Genius Network

Chlorine/CYA relationship

CYA FC relationship question

If you use the Advanced Search box, you will find a wealth of information on this forum that covers this topic.

 

[bluesixer]

Of course - five minutes after I posted this question, I made some progress figuring it out. I'll finish the job with your links.

You've earned a little good karma today.

Many thanks.