FC and relationship to CYA

[vsman]

New to troublefree-
my understanding so far-
- FC is the the active chlorine that does the sanitizing.
- CYA binds chlorine so it is stable under the sun.
- The measured FC is what is NOT bound to CYA.
- If the measured FC is what is NOT bound- why does increasing CYA mean I need a higher FC?

 

[YippeeSkippy]

Because if you don't have enough FC over x amount of CYA, it will ALL be bound to CYA and none available to fight algae.
So you need more than what the CYA will bind up. We know the sun *will* take its daily tax amount of FC no matter what.

Does that make sense?

Use the FC/CYA chart to guide you --> FC/CYA Levels

Maddie

 

[JohnT]

No. All the chlorine is measured by the chlorine test. CYA doesn’t affect the test, only the action of the chlorine in the pool.

 

[Saturn94]

Free Chlorine - Further Reading

www.troublefreepool.com

”What is Free Chlorine in a Pool?
Free chlorine, as measured by a TFP recommended test kit, is the sum of two forms of chlorine in your pool water - active chlorine (the chlorine compounds that directly oxidize bather waste and kill pathogens) and reserve chlorine (the chlorine that is bound to the cyanuric acid stabilizer, or CYA).”

 

[Richard320]

When you measure FC, you are measuring all of it. CYA just acts as a buffer. Think buffered aspirin. It slows the release to prevent upset stomach, but you still get the full amount of aspirin. So it is with CYA. It slows the reaction of the sun on the FC. The FC is still there waiting. But you need a bit extra to be available for immediate action on any algae spores or bacteria in the water.

 

[vsman]

Because if you don't have enough FC over x amount of CYA, it will ALL be bound to CYA and none available to fight algae.
So you need more than what the CYA will bind up. We know the sun *will* take its daily tax amount of FC no matter what.

Does that make sense?

Use the FC/CYA chart to guide you --> FC/CYA Levels

Maddie

kind of makes sense. So when I use a test to measure FC- it is measuring the chlorine bound to CYA and the free associated chlorine?

 

[vsman]

got it... now I understand- thank you.

 

[JohnT]

got it... now I understand- thank you.

That’s what we are here for!