CYA / FC debate

litehowz

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Jun 22, 2022
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Las Vegas, NV
I just passed my CPO exam in order to better understand my residential pool. While I learned a lot more details about chemical disinfection types, measurements and techniques, I don't think I've come any closer to understanding best practices regarding CYA and FC.
Here's my confusion, I'm hoping someone more experienced can help explain:
As I understand, there is a growing argument for keeping CYA levels low to zero. The CDC, local health codes and Model Aquatic Code all recommend low CYA levels, especially in response to a fecal incident. FC needs to be maintained at a higher ppm, for a longer period of time, the higher the level of CYA in your pool. I am told that the state of NY prohibits ANY amount of CYA in public pools.
So, here's my dilemma: I live in Las Vegas- extremely low humidity, high temp, direct sunlight on pool every day. I was told that 90% of FC in pool could be lost in one hour, due to direct sunlight UV radiation. CYA is a way to combat this, and prolong FC in your pool, but has it's downsides, described above.

If the goal is to have a Constant FC level of 2.0 ppm, but low-to-zero levels of CYA, I can't see any way of achieving this without an automatic, constant feeder. What am I missing?

I have a 12,500 gallon pool. I shock with Cal-Hypo 73%. I use Tri-Chlor tabs in a floater, but cannot keep FC sufficient w/ out shocking. I just drained, refilled pool 30 days ago, so high TDS or CYA are not issue. TA=90, CYA=15, pH=7.6.

Any advice would be extremely helpful!!
Mack
 

mknauss

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Welcome to the forum.
There is little debate here on this forum. It is dedicated to residential pool owners management of their own pool water chemistry and maintenance. The forum uses the FC/CYA Chart without discussion.

I will point out that if you use cal hypo in Las Vegas pools, that is close to a crime. The CH rise from fill water alone requires draining the pool every couple years, at least. Softened water should be used for fill water in S Nevada.

Good luck.
 

tim5055

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Yea, many outdated things taught in that class that are based on "how we always do it" rather than following the science.

A former regular participant in this and other swimming pool groups is @chem geek. He has been dealing with this for years and wrote many post here dealing with these issues. He is a member of the Council for the Model Aquatic Health Code (CMAHC), Cyanurate Ad Hoc Committee.

This sentence in this article sums it all up - "The proposal could not be submitted under the committee’s name, since members who produce chlorinated isocyanurates would not be associated with it."

So the committee studied the issue, but was prohibited form publishing their report due to politics, not science. Members who produce tabs and shock objected. So, this shows the industry is not following the science, they are following the dollars.

Council for the Model Aquatic Health Code Considering New Proposal for CYA Levels


If you look around a little you can find the report as the members of the committee had to publish it under their own names rather than as a product of the CMAHC. I'll say it again, politics.


To be honest, you can't follow the teachings of the CPO class and TFP at teh same time. It's impossible.
 

gingrbredman

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I guess I would say that in this forum, where homeowners who want to have a TFP, and safe pool, there are no arguments about CYA and chlorine. There is the TFP way, and there are the other ways.

there is a growing argument for keeping CYA levels low to zero
Not sure I've heard this growing argument here, and this is where I hang out to keep up on the science of my pool chemistry.

If the goal is to have a Constant FC level of 2.0 ppm, but low-to-zero levels of CYA,
Again, this is not the goal of a residential homeowner who wants a TFP, safe, and clear pool, but perhaps a goal of others who are not interested in this.

To be honest, you can't follow the teachings of the CPO class and TFP at teh same time. It's impossible.
Great point! As I said, TFP, or any other way, but you cant chose both, or even parts of each. It is like a lot of new comers who show up, ask a lot of questions and then debate why the pool store advice is different, and want to go that route. Everyone has the choice of how they maintain their pools, and there are a lot of peeps here with a lot of great experience wanting to help, but this forum is very unique and centered around a specific set of protocols, which are very easy by the way, to follow for a TFP! All the old teachings out there are the old way of maintaining a pool. The fact this forum exists to help many with a better way is kind of amazing. Not everyone will embrace it, that's all fine, but I'll stick with the TFP way, thank you very much!
 

AUSpool

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As luck has it I’ve just been brushing up on my favorite FC/CYA literature.
 
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mgtfp

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As I understand, there is a growing argument for keeping CYA levels low to zero.

If the goal is to have a Constant FC level of 2.0 ppm, but low-to-zero levels of CYA, I can't see any way of achieving this without an automatic, constant feeder. What am I missing?

What you are missing is that keeping CYA low to zero is not the right approach.

It is correct that with very high CYA levels, a pool becomes unmanageable. But it also becomes unmanageable with no CYA.

You need a reasonable CYA level, and adjust the chlorine level according to the already mentioned FC/CYA chart. FC basically has to be a certain percentage of the CYA level. FC 5ppm @ CYA 40ppm has for example the same concentration of "active" Chlorine (HOCl) as FC 10ppm @ CYA 80ppm, which is equivalent to less than FC 1ppm with no CYA.

Have a good read through the TFP pool school articles to get the basics. For all the chemical background, go through Chem Geek's sticky threads at the top of the Deep End.

And while I was typing, @AUSpool already posted all the links that I was just about to post.
 
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JoyfulNoise

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Mack,

Unfortunately, taking the CPO class will not help you understand your residential pool better because the CPO is not geared towards a residential pool. The key distinction between a commercial and residential pool is bather load and bather composition. In a single family residential pool, there is only one set of people with a unique set of health issues that uses the pool and they use the pool rarely (low bather load). In a commercial pool, you have hundreds of different bathers all with varying health conditions using the pool. Therefore the bather load is very high and so is the risk transmitting water born illnesses. So commercial pools need to keep their water bodies highly sanitized and they must respond to incidences very rapidly. Recreational water illnesses (RWI’s) are a serious hazard for bathers, not just an inconvenience and so that necessitates a very different set of standards for care. Water treatment for clarity and safety is also very different when you look at a residential pool versus a commercial pool. So the use of CYA is necessarily going to be more carefully scrutinized in a commercial pool setting.

And that’s the crux of it - you can’t apply standards meant for a commercial pool to your own personal pool, it just won’t work.
 
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SoDel

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As a newcomer struggling to understand it all (and it has been fun trying, with much appreciated help, in various ways, from the experts here), the one thing I’d add is always keep an open mind. The old ways of doing things are referred to as the old ways, because new ways were discovered. The present ways will one day be old ways. “A foolish consistency is the hobgoblin of small minds“ a former mentor used to frequently remind me. I’m not sure how doing what works could be made better, but who knows — the earth was flat once and that worked lol.
 

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Bperry

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As a newcomer struggling to understand it all (and it has been fun trying, with much appreciated help, in various ways, from the experts here), the one thing I’d add is always keep an open mind. The old ways of doing things are referred to as the old ways, because new ways were discovered. The present ways will one day be old ways. “A foolish consistency is the hobgoblin of small minds“ a former mentor used to frequently remind me. I’m not sure how doing what works could be made better, but who knows — the earth was flat once and that worked lol.
Be careful with that reasoning. Not all the old ways are worse than the new. Plenty of “new” ways of doing things are detrimental.
 
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dfwnoob

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Something being old doesn't necessarily make it bad, and something being new doesn't necessarily make it better. What matters is the facts. For a good example, look at our understanding of things like cholesterol, fat, partially hydrogenated oils, etc. First they told us we shouldn't use butter because it's full of fat, so we should use margarine. Now we know, whoops, those trans fats in margarine were really bad and actually, eating fat doesn't make you fat. The science changed, and thanks to the continued work and research done by food scientists and dieticians, we got closer to the truth. I wonder how many proposed studies went unfunded because of pressures in the food industry from companies who make margarine. This isn't some wild-eyed tinfoil hat conspiracy, either. My fiancé works in academia and I can tell you without a doubt that anything threatening to the popular political or corporate narrative does not get any money, period.

The CPO training flirts with the truth, but never quite gets there. I wonder why. Maybe looking at the P&HTA's board of directors may shed some light on that. Well, looks like you've got two people on that board (all of them are in the pool industry) with a direct conflict of interest: one is a manufacturer of products like sequestrants and other chemicals. The other runs a company that's basically a Leslies for commercial pools, selling all sorts of snake oil. I can't possibly see how there would ever be industry pressure to keep people like Richard (chem geek) quiet when people like him start coming up with really inconvenient research and data.

Put trust in the independent researchers laying all the data out in front of you, not the industry with $$$ to lose.
 

SoDel

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Easy fellas, I used old and new to distinguish, for example, FC and CYA uncoupled vs CYA/FC ratio, range chemistry vs LSI/CSI, etc. Didn’t intend to imply old is bad (can’t be; I’m old). Was just saying to avoid my way or the highway thinking — open mind stuff.

The point @dfwnoob makes is all I’m trying to point out — consciously reject any potential unconscious bias (or real bias of course) against that which threatens the “institution norms” in whatever form. That”s all — please carry on. :)
 
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JoyfulNoise

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I think it’s important to consider intent and audience when scratching one's head regarding the seemingly conflicted recommendations. TFP is about DIY pool care. The pool industry, with it's various training courses, is about keeping service guys in business and giving them so structure to go by. TFP will NEVER work in the context of a pool service business model - they are giraffes and apples by comparison. Even comparing residential pools to public pools is fraught with difficulty; they are simply different beasts and require different methodologies. So it's all well and good to look through the CPO material or peruse the MAHC documents, but they are largely inapplicable to a private residential pool.

The FC/CYA ratio is nothing more than a handy and easily quantifiable way of talking about the active/sanitizing chlorine level (HOCl/OCl-). If the industry wishes to reduce, or minimize, the use of CYA to achieve a faster kill rate for water-borne pathogens, then the trade-off is water that is harder to control and more harsh to the swimmer. In that case, the priority for infectious disease control outweighs the utility of slowing down chlorine loss or keeping people from having stinging eyes, smelly clothes and/or bleached-out bathing suits. In a residential pool where, 99% of the time, it's just you and your family swimming, that calculus changes dramatically and the residential owner is much more concerned about not having to baby-sit their pool all day and/or having the spouse/kids complain that the water is uncomfortable.
 

duraleigh

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Good thread and good conversation.

We should always define TFP as a teaching forum. We don't teach EVERYTHING but we teach a methodology that works.....hands down.

Our remarkable success and growth over the years tells us that Pool Owners want to learn our methods.

TFP will always be aware that other methods may exist but our real world results are proof positive we are teaching the right things
 

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