CYA debate

[StephenStrum]

I am new to this forum. As a physician-scientist I feel it is imperative to try to understand biological mechanisms and relationships as much as humanly possible. I recently purchased a home with an in-ground pool. The stats re the pool are shown in my signature. As an aside I had a formal pool inspection that indicated high cyanuric acid levels but the inspector did not specifically indicate that this would mandate dumping pool water and replacing with water without CA. The house has a low producing well and city water is not cheap → $400 per 10,000 gallons. I was instructed to completely empty the pool by one pool service person only to learn that that could result in the pool heaving itself out of the ground depending on the height of the water table. Another pool service charging an average of $70-93 per visit said they normally do not test for CH, TA, or CA, even after I explained my current pool chem results. Now the "Great CA Debate".

I spent hours reading various forum discussions (here and elsewhere) on CA. One company manufacturing a chlorinated granular product sold at Costco told me that their product contained no CA (Kem-Tek ALL in ONE), which I later learned was false. All Dichlor and Trichlor has CA in it. Only liquid chlorine or Calcium Hypochlorite products have no CA. Given the issue of water shortage, high cost of water, the pain in the butt to drain part of your pool (in my case half =8,000 gallons), I wondered why pool owners were not told to switch to the non-CA products or even to a liquid chlorine dispenser like the Stenner pump that sense the chlorine level and appropriately delivers the amount of chlorine needed (I would like to start a new thread just on the Stenner pumps).

but now I have come across two papers that state that CA is not an issue at all and that pool drainage is not needed as long as FC levels are 1 ppm to kill bacteria or 3 ppm to kill algae. Clearly I would want both under control so my goal would be 3 ppm. I am giving those that read this thread the URL to the PDF on the paper by Kuechler from 2004 on the Great CA Debate. Here it is

http://tinyurl.com/k2kepej

Another paper is attached to this email on "debunking the chlorine lock myth. Oops. The forum has a max file size of 19 KB. So here is the shortened URL:

http://tinyurl.com/ktxbbsf

There are readable by anyone. The bottom line:

"cyanuric acid levels in excess of 200 ppm had no impact whatsoever on a pool's sanitation provided that the chlorine residual was maintained between 2 and 3 ppm."

The pool water has & remains crystal clear since before I owned the house (during inspection & escrow period) and from Nov to this moment, despite CA levels exceeding 300 ppm and with a 1:4 dilution the CA is 88, which would equate with 352 ppm (explaining why the reading is high when CA is undiluted.

Another issue is measuring TA when CA is high. I have read that one should correct for this by dividing CA by 3 and subtracting that amount from TA. My TA without correction is 208 using LaMotte ColorQ. CA as above divided by 3 = 117. That would mean my corrected TA is 208-117 or 91, which is said to be within the normal range.

Therefore, TWO main issues in this post: 1) the real significance of CA vs bactericidal and algicidal effects and making adjustments on pool chemistry pending other values.

 

[JasonLion]

Re: CYANURIC ACID (CA): The Great Debate

You should call it CYA, not CA. CA is used to indicate calcium. CYA is cyanuric acid.

There is a large amount of mis-information about CYA around. Party this is because companies that sell trichlor have strong financial incentives to continue selling trichlor despite the CYA it contains. But mostly it is because the industry is very slow to adapt to new information. How CYA works has only be known for roughly 50 years, and most simply haven't gotten around to updating their recommendations to match up with current science results.

CYA lowers the effective level of active chlorine and also protects chlorine from sunlight. Our recommendations have you raise the FC level proportionately, so you maintain the same active chlorine level.

The papers you quote simply gets it wrong. You can read about the science behind it various places on the forum. This post is a good place to start. The net result is that the HOCl level is what matters. Not only is the science solid on this, but tens of thousands members of this forum have confirmed the results in their own pool.

While people do often debate the CYA issue, the TA issue is a simple silly mistake. The TA correction you mention is only used when calculating LSI. It serves no other useful purpose. The only number we use on this site is the TA measurement directly from the test kit. That is the one that directly measures the chemical effect of TA, which is what actually matters to a pool owner.

If you really want to get into the science behind this, you should post in The Deep End. If you are happy with the summarized results then this is a good place to talk.

 

[Big Splash]

Re: CYANURIC ACID (CA): The Great Debate

Stephen,

I am also new to the forum and to pool ownership. I am not a scientist. My background is in sales, business and finance. When investigating for myself what is the "best way" to care for my pool and for who should I listen to, my not so trusting nature and business experience told me to check things out. More so, I asked myself who's got skin in this game. It's a "follow the money" and you'll get the right answer for the method that works for me. The experts here will chime in soon. But, I think they'll tell you that paper you've referenced is flawed. How do know who's right? Well, I don't think it's anyone on this forum is making a ton of money (like Occidental Chemical Corporation) on offering free advise. So make up your own mind.

Good luck.
Anyone got popcorn?

Jason beat me

 

[Butterfly]

Re: CYANURIC ACID (CA): The Great Debate

Good luck.
Anyone got popcorn?

::


Moving to the deep end

 

[JohnT]

Re: CYANURIC ACID (CA): The Great Debate

Another issue is measuring TA when CA is high. I have read that one should correct for this by dividing CA by 3 and subtracting that amount from TA. My TA without correction is 208 using LaMotte ColorQ. CA as above divided by 3 = 117. That would mean my corrected TA is 208-117 or 91, which is said to be within the normal range.

You need to remember that TA is not a measurement of a quantity or concentration of something in the water, but rather a test of the buffering action of the water, with the results expressed in mg/L as CaCO₃. A TA of 100ppm doesn't mean that there is 100ppm of any particular mineral in the pool, but that the water buffers just like it would if it had 100mg/L of CaCO₃.

Since it is an observation of the buffering ability of the water, it doesn't matter what actually provides the buffering, only that it is there. Subtracting the CYA level from the TA reading makes no sense for buffering purposes.

When it is subtracted for saturation index purposes, it is to produce a more accurate indication of the alkalinity due to carbonate and bicarbonate ions in the water, which impact scaling. Water with very high CYA and moderate in carbonate ion concentration isn't as likely to create scaling as water that is higher in actual carbonates and lower in CYA, even though their TA reading may be the same. Adjusting the high CYA water's TA makes for a more accurate saturation index calculation.

 

[chem geek]

As a physician-scientist, you should be aware that peer-reviewed papers in respected scientific journals are a far better source for factual information than what a manufacturer of chlorinated isocyanurate chemicals (e.g. Trichlor, Dichlor) puts out.

For your first link on "The Great CYA Debate 2004", written by a chemist at Occidental Chemical Corporation (OCC), I wrote extensively in this thread about the Pinellas County study referred to in that report. The bottom line is that bacteria are very easy to kill faster than they reproduce so that is not a good indicator of whether high CYA levels are a problem. Algae are harder to kill and require higher active chlorine levels. Also, to kill bacteria faster to prevent person-to-person transmission of disease one needs a higher active chlorine level so the algae inhibition rate is a decent level for both. The studies just showed that SOME CYA has benefit, but they did not prove at all that a high CYA was OK. In fact, having some CYA is better than no CYA because with no CYA the active chlorine level is TOO strong unless one maintains a very low FC and that is simply impractical to do. I've communicated and met with Thomas Kuechler before but you need to keep in mind that both studies are with commercial/public pools generally with high bather loads. In such pools there is often a lot of ammonia from sweat and urine and this forms monochloramine and that is algaecidal (and also kills bacteria, albeit slowly). Also, as you can tell from my Pinellas County thread, no one bothered to look at hypochlorous acid (HOCl) concentration to see that it is at least as good a correlate as FC, even better if one looks at more than just controlling bacterial growth (i.e. algae growth). This is not the same situation as with a residential pool which is low bather-load.

The second link from Bio-Lab, makers of stabilized chlorine (Trichlor, Dichlor) products, says that in the presence of ammonia that bacteria are still killed even at high CYA levels. That's true because with ammonia the chlorine combines with it to form monochloramine very quickly (in under a minute even when CYA is present). However, monochloramine kills more slowly so while this may be OK for preventing uncontrolled bacterial growth, that's not the same thing as having faster kill times to prevent person-to-person transmission of disease and more importantly for residential pools, to prevent algae growth. Also, residential pools are low bather load so have very little ammonia introduced so very little monochloramine. This is why we have thousands of members posting on this forum about problems with their pools when their CYA gets high (if they don't proportionally raise their FC level) and they then learn the truth about the chlorine/CYA relationship.

If you want to see the links to peer-reviewed scientific papers in respected journals, then read the "Chlorine/CYA Relationship" section in the first post of the thread Certified Pool Operator (CPO) training -- What is not taught.

By the way, for your particular pool you can have a high CYA level and not have problems with algae or cloudy water because you may be lucky enough to have water with very low phosphates (or nitrates, but usually there are nitrates from oxidized bather waste). The use of phosphate removers or algaecides are some of the ways of managing a pool with high CYA, but the least expensive approach is usually to just maintain the proper FC/CYA ratio to prevent green and black algae growth and for practical purposes that means keeping the CYA <= 80 ppm. You would mostly use chlorinating liquid or bleach since that doesn't raise Calcium Hardness (CH) like Cal-Hypo nor does it raise Cyanuric Acid (CYA) like Trichlor and Dichlor.

I'll be happy to answer any questions that you have after you have thoroughly reviewed all of these sources of information I have given to you.

 

[StephenStrum]

Thanks for the replies above. I did do many Pubmed searches but CYA is almost always not part of the title. I just performed the same search with cyanuric acid being mentioned in the abstract and found 402 papers between the years 2000 and 2014. I just finished scanning the titles of these peer-reviewed publication(s) to see what is possibly relevant. I found 8 papers with some (usually remote) reference to CYA in swimming pools:

Centers for Disease C, Prevention: Pseudomonas dermatitis/folliculitis associated with pools and hot tubs--Colorado and Maine, 1999-2000. MMWR Morb Mortal Wkly Rep 49:1087-91, 2000

Dufour AP, Evans O, Behymer TD, et al: Water ingestion during swimming activities in a pool: a pilot study. J Water Health 4:425-30, 2006

Koh G, Gui EM, Teo TL, et al: Determination of cyanuric acid using exact matching isotope dilution mass spectrometry. J Sep Sci 36:1054-60, 2013

Montgomery W, Crowhurst JC, Zaug JM, et al: The chemistry of cyanuric acid (H3C3N3O3) under high pressure and high temperature. J Phys Chem B 112:2644-8, 2008

Shippert BW: Pool chemical blast injury. Ann Emerg Med 55:370-2, 2010

Dorevitch S, Panthi S, Huang Y, et al: Water ingestion during water recreation. Water Res 45:2020-8, 2011

Liu X, Parales RE: Bacterial chemotaxis to atrazine and related s-triazines. Appl Environ Microbiol 75:5481-8, 2009

Modh RP, De Clercq E, Pannecouque C, et al: Design, synthesis, antimicrobial activity and anti-HIV activity evaluation of novel hybrid quinazoline-triazine derivatives. J Enzyme Inhib Med Chem 29:100-8, 2014

I have not read the abstracts of these papers nor yet checked to see if any are free full text. You can see from the titles that I was very generous insofar as these 8 papers I culled from the 402.


Meanwhile I have downloaded most of the papers hyperlinked in the post by Chem Geek. One appears to be written in French but I have ordered it anyway since the abstract does not relate the results of the research. I will review the other papers that were full text downloads via the hyperlinks "here, here, etc".

I will be a lot more medically oriented in researching CYA and its relationship to ID (infectious disease), as well as the pool chemistry involved. I can see that this is not a light task as I mistakenly believed in my earlier post. I am still actively practicing medicine (oncology) with a focus on PC (prostate cancer) so I do not have a great deal of free time.

I will continue to drain pool water to reduce CYA levels while I am trying to assimilate all this information. Meanwhile my pool is clear, with FC 3.63, TC 3.63, pH 7.7, TA 208, CH 438, and CYA (using a 1:4 dilution) 88, or 88x4 = 352. Note I am not using what appears to be the preferred test kit by most forum members (Taylor) but the ColorQ by LaMotte, which I had already purchased before joining this forum.
Watching the videos of various testing, the Taylor kit looks far more onerous and subjective, at least to me. I will try to master the science of pool water maintenance and testing.

 

[chem geek]

Thanks for your search for papers. The few that are about problems in commercial/public pools or hot tubs are invariably due to very high CYA levels or very low FC/CYA ratios (the first paper you listed had < 1 ppm FC with 40-60 ppm CYA), not the normal levels we recommend. Too much of anything is usually not good -- as a physician I'm sure you've heard of the adage from Paracelsus that "the dose makes the poison". Too much ordinary table salt will kill you. So one link that isn't in what I gave you already is this one that says that CYA has an insignificant amount of skin absorption. It is likely that the chlorinated isocyanurates (chlorine bound to CYA) likewise have minimal skin absorption. This link gives the toxicology of CYA with an LD₅₀ (rat) of 7700 mg/kg (table salt is 3000 mg/kg so even more lethal) and an NOAEL of of 150 mg/kg/day which with 80 mg/L in the pool would require a 50 kg person to drink nearly 94 liters (nearly 25 gallons) of pool water every day and still be at the no observed adverse effect level. So you can pretty much ignore CYA toxicity with respect to pool water. In fact, the "Water ingestion during water recreation" paper actually uses cyanuric acid measurements in urine to determine the amount of pool water (that has CYA) that is ingested (i.e. CYA acted as a tracer chemical). It basically passes through the body with minimal degradation or absorption (which helps explain its low toxicity).

In the links I gave to you the most important is the one to the 1974 O'Brien paper that definitively determined the equilibrium constants for chlorine and the various chlorinated isocyanurates (chlorine bound to CYA). The other links in that same "Chlorine/CYA Relationship" section show that this equilibrium relationship predicts the effects of the significantly reduced hypochlorous acid (HOCl) concentration. Fortunately it takes a very low active chlorine level to kill bacteria and prevent algae growth. We set our active chlorine guideline to that which prevents green and black algae growth in pools regardless of algae nutrient (phosphate, nitrate) level. Algae growth is ultimately limited by sunlight and temperature. If you are interested in pathogen kill times when the FC is roughly 10% of the CYA level (roughly equivalent to 0.1 ppm FC with no CYA) then see the table in this post.

You'll also find the link to the derivation that the active chlorine level is roughly proportional to the FC/CYA ratio. So 3 ppm FC with 30 ppm CYA, 6 ppm FC with 60 ppm CYA, and 9 ppm FC with 90 ppm CYA, all have the same active chlorine level so prevent algae the same and have the same disinfection and oxidation rates. Understanding that the active chlorine level responsible for disinfection and (most) oxidation is proportional to the FC/CYA ratio is key to understanding how to properly manage a pool. Clearly one cannot continue to use solely stabilized chlorine (Trichlor, Dichlor) products in a longer swim season since the CYA level will build up too high to be impractical to have a high FC level to compensate. One can, of course, use algaecides or phosphate removers to help prevent algae growth, but these are extra cost and don't compensate (much) for killing bacteria to prevent person-to-person transmission of disease nor do they compensate at all for the rate of oxidizing bather waste (mostly nitrogenous compounds from sweat and urine). That's why we recommend using chlorine alone whenever possible at an appropriately maintained FC/CYA ratio as it handles disinfection, oxidation, and prevention of algae growth.

 

[Isaac-1]

For one of many threads on why we generally don't like the Color Q see this link which sums it up nicely 8 messages down from the top http://www.troublefreepool.com/threads/63563-Colorq-pro-7-debate-and-results

 

[Big Splash]

I will be a lot more medically oriented in researching CYA and its relationship to ID (infectious disease), as well as the pool chemistry involved. I can see that this is not a light task as I mistakenly believed in my earlier post. I am still actively practicing medicine (oncology) with a focus on PC (prostate cancer) so I do not have a great deal of free time.

Back to topic... The side conversation has been moved here. JasonLion

Stephen, I'm sure folks would appreciate your work.

Otherwise, we'll have to get these guys...