Chlorine & CYA levels in SWG versus Liquid Chorline

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G

gorji

Active member
Jun 11, 2014
34
Syracuse, NY
Hi: Why is the FC required for adequate algae control is different for SWG pools versus those using liquid chlorine? Or perhaps I should ask why is CYA levels allowed to be higher in SWG pools compared with the pools chlorinated by liquid chlorine?

Thank you and appreciate the response.
 
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G,

Really we are talking about two different things..

The recommended CYA level for non-saltwater pools is really adjustable base upon where you live. Pool owners in the north could use a little less and those in the south often use much more. It is not a fixed number that you are required to use, it is a good starting point.

The FC level for a non-saltwater pool is assuming that you are adding Liquid Chlorine once a day, so that chlorine has to last until you add more chlorine the next day, so it is a little higher.

The FC level for a saltwater pool assumes that the SWCG is adding a little chlorine over a long period of time, so the recommended level can be lower.

The recommended CYA level for saltwater pools is a little higher as we would like to reduce the amount of FC that is burned off by the sun. This allows the cell to last longer.

These levels are just guidelines that seem to work pretty well for most pool owners. That said, the real key is always keeping your FC and CYA in the proper relationship. You can mix and match these levels all you want based on where you live, and how much effort you want to use to maintain your pool.

Thanks,

Jim R.
 
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Trying to digest the statements above which I appreciate. "The recommended CYA level for saltwater pools is a little higher as we would like to reduce the amount of FC that is burned off by the sun. This allows the cell to last longer." is intriguing since while saving the SWG, we allow higher CYA which makes the need for higher free Cl.
 
gorji said:
Trying to digest the statements above which I appreciate. "The recommended CYA level for saltwater pools is a little higher as we would like to reduce the amount of FC that is burned off by the sun. This allows the cell to last longer." is intriguing since while saving the SWG, we allow higher CYA which makes the need for higher free Cl.
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But its a one time bump & then the swg just needs to maintain what is lost each day. For instance if I have 60ppm cya in the middle of the summer I will lose 4-5ppm/day every day. If I raise my cya to 80 I will only lose 3ppm/day & then I dose 1 time to high target with liquid chlorine & my swg only has to produce 3ppm each day. I hope this helps with understanding.
 
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gorji said:
Loss of 4-5 ppm/day is due to what? Rain, Splash out of pool...?
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Generally, loss is due to chlorine killing organics plus any additional products added by swimmers like oils, lotions, etc. The lower the loss the better. If there is no swimming and you loose more than 4 ppm in 24 hrs, you may need more CYA to protect the chlorine. Often times it's best to do an Overnight Chlorine Loss Test before increasing the CYA to ensure there is no algae.
 
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gorji said:
Thank you for the above @Mdragger88. Clarification needed for simple people like myself: Loss of 4-5 ppm/day is due to what? Rain, Splash out of pool...?

thank you
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As Pat said, organics & contaminants that get constantly introduced to the pool via the environment & swimmers as well as uv comsume fc daily.
 
This has me thinking about Trichlor and CYA levels. I will need to use Trichlor in an inline feeder while on vacation this summer. It should distribute chlorine like a SWG. During that time, FC could be lowered.
 

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mfifield01 said:
It should distribute chlorine like a SWG. During that time, FC could be lowered.
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When on vacation with no ability to test and jump on any possible problems immediately it's smart to run hot with the FC levels, not lower them down to the absolute bare minimum. And how do you intend to keep them at those levels when you can't test and adjust the output? Trichlor isn't nearly as consistent as an SWG.
 
mfifield01 said:
This has me thinking about Trichlor and CYA levels. I will need to use Trichlor in an inline feeder while on vacation this summer. It should distribute chlorine like a SWG. During that time, FC could be lowered.
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what you’re implying might be somewhat true if you were
#1 - feeding the pool around the clock &
#2 - it wasn’t Trichlor which adds .5 ppm cya with every 1 ppm of fc it adds thus increasing the necessary fc minimum at a quick pace
I suggest for your vacation you raise fc higher than target 🎯 in tandem with using the feeder.
 
Mdragger88 said:
what you’re implying might be somewhat true if you were
#1 - feeding the pool around the clock &
#2 - it wasn’t Trichlor which adds .5 ppm cya with every 1 ppm of fc it adds thus increasing the necessary fc minimum at a quick pace
I suggest for your vacation you raise fc higher than target 🎯 in tandem with using the feeder.
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It is feeding the pool in the exact same manner as the SWG. Anytime the pump is on chlorine is coming from the inline chlorinator.

The amount is not significant. In the period of time, I would need to change my FC by 1 due to an increase in CYA.

I have been running lower on CYA knowing that I need to use Trichlor. This bump will help me get to 60.
 
Donldson said:
When on vacation with no ability to test and jump on any possible problems immediately it's smart to run hot with the FC levels, not lower them down to the absolute bare minimum. And how do you intend to keep them at those levels when you can't test and adjust the output? Trichlor isn't nearly as consistent as an SWG.
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I won't be able to adjust while gone. I can probably get my father to check the levels. I plan to up the FC to about 15 with LC before I leave. Based on Pool math, I'll need 6 tabs to maintain my current FC loss of 3 each day.

Trichlor in my inline chlorinator has been really consistent. I've used it in the spring to get my CYA levels up. I was able to maintain an FC of 5 each day.
 
mfifield01 said:
It is feeding the pool in the exact same manner as the SWG. Anytime the pump is on chlorine is coming from the inline chlorinator.

The amount is not significant. In the period of time, I would need to change my FC by 1 due to an increase in CYA.

I have been running lower on CYA knowing that I need to use Trichlor. This bump will help me get to 60.
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You should use the manually chlorinated chart/values- not the swcg values to ensure you don’t end up with a problem.
A little extra fc is not an issue, too little fc has many downsides.
 
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I personally run my fc at 10% of my cya all the time - swg or not. (Except on vacation when I raise to slam level)
This ensures I don’t broach minimum even if events occur like power failures, parties, torrential rains, very high uv days etc. before I can deal with them & adjust.
 
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Mdragger88 said:
You should use the manually chlorinated chart/values- not the swcg values to ensure you don’t end up with a problem.
A little extra fc is not an issue, too little fc has many downsides.
Click to expand...
I would disagree if an inline chlorinator can keep up with the FC of a SWG. If it were possible to use Trichlor all the time, I would follow the SWG chart. Distributing Trichlor is almost the exact same (pump run dependent and set level). I do plan to keep my FC higher, since it's not worth the risk.
 
There are other factors that influence the swcg fc/cya recommendations here, like the processes/reactions that occur inside the cell.
More about that can be found in the deep end.

The Deep End...

Pondering the deep mysteries of pool chemistry? Plunge into the more technical aspects of pool care. Discussions here may not be applicable to everyday pool care.
www.troublefreepool.com www.troublefreepool.com
 
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