What's the reasoning behind a higher CYA level recommendation from TFP?

[Econdron]

I hope this doesn't come across as un-trusting, or arrogant, I'm just trying to learn. I came across this article from Orenda Tech last night, and it seems to directly contradict the recommendations from TFP:

Minimal CYA | Pillar 4

Pillar 4 is Minimal Cyanuric Acid (CYA). CYA (aka Stabilizer or Conditioner) protects free chlorine from sunlight. Some CYA is good, but too much is bad.

blog.orendatech.com

TFP says I should have my CYA at about 80ppm, the link above says that will put my chlorine at being pretty much completely ineffective. If I understand correctly, TFP just recently even increased their recommendations for how much CYA a pool should have. Again, not trying to step on toes here, just trying to understand and learn.

 

[Flying Tivo]

We recommend a science based Ratio FC/CYA Levels so it depends on what level of CYA you are or want to be. This ensures you have available FC to kill pathogens. At least we agree on the 7.5% ratio, personally i manage at 10% ratio.

 

[Econdron]

I find it really interesting they quote Richard Falk @chem geek in the Orenda article, but if I understand correctly, he is the one who developed the TFP FC/CYA chart?

 

[Texas Splash]

TFP says I should have my CYA at about 80ppm, the link above says that will put my chlorine at being pretty much completely ineffective. If I understand correctly, TFP just recently even increased their recommendations for how much CYA a pool should have. Again, not trying to step on toes here, just trying to understand and learn.

I will also add that for a salt pool, the recommendation has been 70-80 for quite a long time. A lower CYA (i.e. 60) may not be typically recommended, but may be suitable for pools in cooler climates where the sun isn't as intense as it is in AZ, TX, FL, etc.

Also see:

CYA Chlorine Relationship - Further Reading

www.troublefreepool.com

 

[Holydoc]

Also if you read the article, it basically sums up the amount of FC you need per given CYA. The bottom line is that you need 7.5% of your CYA in FC to prevent algae. That is exactly how the FC/CYA tables were developed. So the article you quoted basically is supporting this forum's recommendations.

 

[Econdron]

Is the TFP goal to get the staying power of chlorine at 100%? I'm just looking at the chart on the Orenda link. 30ppm CYA is about 96%, 70ppm is about where it hits 100%.

Is the idea that CYA is relatively cheap and only a one-time added chemical and it saves a lot more in salt usage generating FCL if the CYA is higher?

 

[Flying Tivo]

Is the idea that CYA is relatively cheap and only a one-time added chemical and it saves a lot more in salt usage generating FCL if the CYA is higher?

Salt is not used up on a Salt water chlorinated pool. Its a cycle. We recommend higher cya in salt water pools because FC is produced slowly by the cell and not a one time addition as manual chlorinated pools. CYA is rather cheap but could have been expensive and we would still use it, as there is no other product similar. We do have Bromine that plays a similar role but lot more expensive and less efficient in maintaining a sanitary pool aand difficult to test.

 

[Econdron]

So the recommendation is to have a CYA of 70-80ppm so that the SWG can keep up with necessary level of FCL as a lower CYA risks the SWG not being able to produce enough FCL to keep up with the loss of chlorine from sunlight? Is that accurate?

 

[Flying Tivo]

CYA risks the SWG not being able to produce enough FCL to keep up with the loss of chlorine from sunlight?

SWG produce chorine according to whatever setting. CYA does not help or deter the SWG from producing. UV and organics are the main FC killers. CYA just helps protect FC from UV and have it readily available to kill organics when needed. Think of it as a Reserve but ready for action.

 

[Econdron]

So if I were to drop my CYA down to 30ppm and keep my FCL at 6ppm, what are the drawbacks/consequences in that case? The SWG would need to be set to a higher setting to account for additional lost FCL to UV?

 

[Oly]

At 30ppm CYA your salt cell would work harder to make up for the increazed FC loss due to solar radiation. The upside is if for any reason you do get an algae outbreak a lower CYA will make the SLAM less costly. Monitor your daily FC loss as you raise CYA by 10ppm to find your sweet spot. I like 60ppm for my system.

 

[mknauss]

Whatever Orenda says, I challenge someone in Texas or Arizona to keep their CYA at 15 ppm (which cannot be measured) and 1 ppm FC. That is what they are implying. If my CYA goes from 70 to 60, my FC loss jumps by nearly 50%. Your SWCG would have to be really oversized and generating a lot per day to keep up at the low CYA.

 

[duraleigh]

First, In a Chicago climate, I would suggest a CYA of 60 ppm to start. Then, adjust upward only if you feel your FC consumption is excessive.

Our suggested guidelines are based on the real-world experiences of thousands of pool owners in different climates and these guidelines are just that.......guidelines. Not hard and fast rules.

So if I were to drop my CYA down to 30ppm and keep my FCL at 6ppm, what are the drawbacks/consequences in that case? The SWG would need to be set to a higher setting to account for additional lost FCL to UV?

That is correct. In fact you can drop your CYA to zero if you like and your only consequence will be rapid depletion of chlorine........so much so that your SWG may not be able to make enough chlorine and you will have an unsanitary pool and a quickly burned up SWG.

So, it's a trade off. The more CYA in your pool, the more FC you save from depletion but only up to a POINT. CYA above 80 becomes barely manageable and, in general, simply does not work well. CYA much below 50 usually does not save much FC so there is little "return on investment"

The choice goes to each homeowner to follow Orenda's (or anyone else's) advice or perhaps absorb the collective wisdom of thousands of pool owners here on TFP. The guidelines we suggest are the result of real world experience and, best of all, we prove daily they work

 

[BB_Mike]

I came here today with the same question. My pool store says that a CYA over 50 will cause "chlorine lock" and made it sound like FC would not be available to fight bacteria. My AGP manual also says not to exceed 50 for CYA.

Is there a skin/eye side to this? Will my skin or eyes notice 8ppm FC versus 4ppm if each had their respective CYA amount?


My SWCG is slow to make chlorine. It's an Intex with a SWCG of 11 grams/hr. For my 8500 gallon pool, their manual says it should run 5 hours. Even with CYA of 40, I cannot manage more than 2ppm of FC and that's running 10+ hours a day. So now I am set on supplementing chlorine with liquid bleach as a crutch for the SWCG. But now I have the power to overdue it! So I am getting more smart on CYA.

Thanks.

 

[IceShadow]

I came here today with the same question. My pool store says that a CYA over 50 will cause "chlorine lock" and made it sound like FC would not be available to fight bacteria. My AGP manual also says not to exceed 50 for CYA.

Is there a skin/eye side to this? Will my skin or eyes notice 8ppm FC versus 4ppm if each had their respective CYA amount?


My SWCG is slow to make chlorine. It's an Intex with a SWCG of 11 grams/hr. For my 8500 gallon pool, their manual says it should run 5 hours. Even with CYA of 40, I cannot manage more than 2ppm of FC and that's running 10+ hours a day. So now I am set on supplementing chlorine with liquid bleach as a crutch for the SWCG. But now I have the power to overdue it! So I am getting more smart on CYA.

Thanks.

It's all about the FC/CYA ratio, which is what equipment manuals, pool stores, most internet forums and Facebook groups, etc. don't recognize.

CYA of 30ppm with a FC of 12 is MUCH less harsh on eyes/skin/equipment/bathing suits than a FC of 3 with a CYA of 0. It's all about the hypochlorous acid that is free in the water (HOCl). CYA binds it up, and the same amount of HOCl is present in water with the same FC/CYA ratio, whatever the actual numbers may be.

Raise that CYA up to 70 and your FC will hold better. Your target will be higher, but the sun will eat less of it. (You may also want to do an Overnight Chlorine Loss Test just to be certain that you're not losing FC to algae hiding somewhere in the pool, to be safe.)

 

[mgtfp]

It looks like Orenda is picking raisins from multiple bowls. But raisins all on their own don't make a meal.

They are quoting Chem Geek when it gets to active chlorine levels vs. CYA. His conclusion from these graphs was that FC has to be adjusted to the CYA-level, keeping the FC/CYA ratio constant.

And then they are bending the CDC's recommendation

If there is an accidental fecal release (AFR) in a commercial pool, the CDC’s recommendation is a maximum of 15ppm CYA

to

With CYA over 15ppm, disinfection becomes not only impractical, but it also becomes virtually impossible. Sure, you could do it, but the levels of free chlorine and time that would be needed are insane.

A fecal accident in a commercial pool is a completely different thing to maintaining a residential pool that is only used by family and friends. A few of them, not hundreds or thousands of them. You know them, and they try really hard not to poop in your pool.

Yes, if you are suspecting crypto, you need - if the problem is to be solved with chlorine - very high HOCl levels that you can't achieve within regulations applicable to commercial pools limiting max allowable FC-levels, when there are higher levels of CYA in the water.

They are even citing Chem Geek's article Assessing the Impact of Cyanuric Acid on Bather’s Risk of Gastrointestinal Illness at Swimming Pools.

Well, the conclusion from that article is not to limit CYA to 15ppm. The conclusion is

A maximum CYA/FC ratio of 20 is recommended.

Edit: And this recommendation is purely based on keeping a pool sanitary. This article is not even mentioning algae, which is usually a bigger issue in residential pools, which is why TFP is recommending lower CYA/FC ratios (or higher FC/CYA ratios, same thing).

 

[DrewLG]

I hope this doesn't come across as un-trusting, or arrogant, I'm just trying to learn. .... TFP says I should have my CYA at about 80ppm, the link above says that will put my chlorine at being pretty much completely ineffective.

Nothing wrong with questioning the TFP guidance. You SHOULD do that.

I've read the Orenda article and I don't see where they say that at 80ppm your chlorine will be ineffective. Can you point me to the passage you're referring to?

Meanwhile, the article seems to be written for commercial or public pool operators, whose risks and requirements are very different from residential pool owners.

For residential pool owners, the seemingly rhetorical questions Orenda asks in the article have answers that don't match what they're implying:

CYA dramatically plummets the percentage of strong chlorine (HOCl). What do you think that does to your sanitizer's strength?​

It does nothing terrible. Without CYA, I'd only be able to put a max of around 4ppm FC in my pool without causing severe bather discomfort. That would give me many times more HOCl than I need to keep my pool sanitized and algae-free -- at first -- but it would quickly fade and need to be replenished hours later. By adding CYA, I can raise my FC to 8 ppm (or even 20 ppm) without causing discomfort -- because only a small percentage of FC at a time is present as HOCl -- and that will give me around 2x-3x the necessary level of HOCl, which will fade very slowly and not need to be replenished for at least a day. CYA wins.​

​

What does that do for the killing power of chlorine?​

It slows the process. But that's ok, because the chlorine still kills faster than bacteria and algae can multiply. So it disinfects as completely as if there were no CYA in the water.​

​

So if you have 100 ppm CYA, which is not uncommon at all, your new minimum free chlorine to prevent algae is 7.5 ppm! Can you sustain that?​

Of course I can. I have 50 ppm CYA in my pool now, and I maintain around 8 ppm FC. It's no trouble whatsoever, since all I have to do is keep ahead of the FC loss, which is only around 2 ppm/day for FC between 4 ppm and 16 ppm.​

​

With CYA over 15ppm, disinfection [of Cryptosporidium specifically, not other parasites or bacteria or viruses] becomes not only impractical, but it also becomes virtually impossible. Sure, you could do it, but the levels of free chlorine and time that would be needed are insane.​

It's true that if someone with diarrhea swam in my pool and infected it with Cryptosporidium, it would take days of SLAM levels of chlorine to be sure that at least 99.9% of it was killed. But a) nearly everyone who swims in my pool lives with me, so if they're sick I'm probably also sick anyway, b) everyone who swims in my pool knows not to do so if they have diarrhea, c) if there were an incident, I can close my pool and superchlorinate it for a week, no problem. Wouldn't even cost more than a good dinner.​

 

[mgtfp]

I've read the Orenda article and I don't see where they say that at 80ppm your chlorine will be ineffective. Can you point me to the passage you're referring to?

As I mentioned above, they've completely bent the actual CDC recommendation.

 

[mgtfp]

Another thing. They start blubbering on how CYA affects CSI, without discussing whether that's good or bad. And then that:

 

[Katodude]

So not scientific but my experience this year. I had a pool leak, that coupled with some very warm pool water and a lot of business travel caused my to drop to almost 0 CYA. Let’s call it 10 since it was slightly cloudy when the vial was filled. At that rate my SWG could not keep up and I got algae. A SLAM got rid of that. After making sure I passed two OCLT, it was time to add CYA to the pool. I added 10ppm per day and measured FC twice a day. Now my pool gets full Florida sun all day long.

With 10ppm of CYA my FC loss during the day was around 9 or 10ppm. SWG could not keep up I had to dose with liquid to supplement.

As I added CYA each day the daily drop in FC kept coming down. But until I got to about 70ppm the SWG generator could not keep up. Once I got to 80 the pool became super easy to manage and I could even reduce the output of the SWG.