Cya / FCl table

[UKjames]

I was looking to refresh my memory on cya and fca ratios.

So looked for the “table” but see it’s gone now.
Personally I found it useful but this thread is still accessible.

Chlorine/CYA Chart

EDIT: You will find a simplified and standardized version of this chart at Pool School, Chlorine / CYA Chart. Chlorine/CYA Chart by Chemgeek FC = Free Chlorine in parts-per-million (ppm) CYA = Cyanuric Acid in parts-per-million (ppm) CYA ........... Min FC3 ..... Target FC ...... Yel/Mstrd...

www.troublefreepool.com

I’d forgotten the 7.5 pct and 4.5pct for SWCG pools which I think is really handy when doing a quick check on whether the current FCL level is ok.

One question, why doesn’t poolmath return 40pct for low CYA level SLAM? My pool is sort of indoor so I don’t run high CYA level.

 

[needsajet]

CYA levels can be reliably measured down to 30 ppm CYA by the recommended test kits, so that's a limitation of Trouble Free Pool Care. It's minor because 30 ppm CYA has enough benefits that's it's also useful for indoor pools.

So the SLAM is designed to work as part of TFPC which is in the reliable (enough) testing range of 30 ppm to 80 ppm CYA.

Nice to meet you via TFP

 

[UKjames]

Thanks! I have been using pucks to increase my cya but then got a bit worried about the concentration of acid getting too great around the floating duck and damaging the liner if I only run the pump once a day.

 

[needsajet]

Floaters are pretty effective. You might be able to tie it some spot or in some way to hold it away from the liner. Mind the CYA level over time, as you've been doing. Good stuff. The other option is to just use stabilizer and set the CYA at the level you want, e.g. 30 ppm CYA

 

[Newdude]

So looked for the “table” but see it’s gone now

Screenshot these and you won't even need to log in to see them.

 

[Mdragger88]

The old quick chart is gone but you can always use the new tool
FC/CYA Levels
PoolMath app & webpage PoolMath
lists all cya levels 20 & below have a slam value of 10ppm. So this is what is suggested to use at those cya levels. I can only assume this is because it’s not possible to accurately measure cya below 20 ppm so this errs on the side of ensuring the slam is effective if you actually do have some cya but just can’t tell.

 

[UKjames]

Thanks all. It was the slam of 10 in pool math for cya 20 that I was questioning. 40pct would imply slam 8. Cya 30 has slam 12 in pool math which ties to 40pct. I think I need to get my cya up to 30 and then I’ll be ok with the charts.