Chlorine/CYA Chart comments

[thepoolpros.com]

Split off of Chlorine/CYA Chart. JasonLion

Im not sure the relavence of this chart. the key is to protect the chlorine that you put into the pool. 10 ppm of cyanuaric acid will protect 1.5 ppm of chlorine from the UV destruction of the Chlorine Molecule. The 1/2 life of Chlorine when unprotected is 1 hour. By adding stabilizer it will greatly decrease your cost to operate your swimming pool.
So if you want to keep 10ppm of Cl2 in your pool, you should have a cyanuaric level of atleast 70 ppm. Because of the added benefits as an algacide and ph buffer i recommend to keep the stabilizer as high as possible. In Florida with concrete or gunite pools, I recommend a stabilizer of atleast 100ppm and a max lmit of 400ppm.

I wrote a piece about this on my website.

 

[dmanb2b]

Re: Chlorine/CYA Chart

I recommend a stabilizer of atleast 100ppm and a max lmit of 400ppm.

I wrote a piece about this on my website.

That is by far poor water chemistry advice. Please take the time to read through pool school before deciding to post advice that is contradictory to what we would have advised. There is not problem with doing so, but you'll have to back up your statement's with facts. With CYA at 100+ it becomes almost impossible to properly shock a pool.

 

[Ohm_Boy]

Re: Chlorine/CYA Chart

Yeah, I can see a problem with that. CYA does protect the chlorine, but it tends to reach a point where it protects the chlorine from doing any sanitizing or oxidizing as well as protecting it from UV degradation. You end up needing higher and higher FC levels to get any work out of it, 'cause it's all bound up by the CYA buffer.

 

[chem geek]

Re: Chlorine/CYA Chart

Im not sure the relavence of this chart. the key is to protect the chlorine that you put into the pool. 10 ppm of cyanuaric acid will protect 1.5 ppm of chlorine from the UV destruction of the Chlorine Molecule. The 1/2 life of Chlorine when unprotected is 1 hour. By adding stabilizer it will greatly decrease your cost to operate your swimming pool.
So if you want to keep 10ppm of Cl2 in your pool, you should have a cyanuaric level of atleast 70 ppm. Because of the added benefits as an algacide and ph buffer i recommend to keep the stabilizer as high as possible. In Florida with concrete or gunite pools, I recommend a stabilizer of atleast 100ppm and a max lmit of 400ppm.

I wrote a piece about this on my website.

I'm sorry, but it doesn't work at all the way you described. CYA is not an algaecide -- if it were, you wouldn't have literally hundreds of pool owners coming to this site with algae problems in their pools every year when their CYA levels get high and they don't maintain an appropriately high FC level for that CYA level. If you want an additional pH buffer, use 50 ppm Borates (and they are also a mild algaecide).

There is a chemical relationship between chlorine and CYA that has been known definitively since at least 1974 as described in this paper. CYA protects chlorine from breakdown from the UV in sunlight in two ways. First, most of the chlorine combines with CYA to form compounds (called chlorinated isocyanurates) that are resistant to breakdown from UV -- they do breakdown, but more slowly. Second, the CYA itself can absorb UV to somewhat shield lower depths, though this is a secondary and less dramatic effect (though is still noticeable in many pools as one gets towards 80 ppm CYA). Unfortunately, chlorine combined with CYA is for practical purposes not a sanitizer or oxidizer so it is only the small amount of unbound chlorine that does all the work to kill pathogens and prevent algae growth.

I don't understand your recommendation to keep the CYA level at least at 100 and no more than 400 ppm in light of your article on Chlorine Lock where you state "Do not keep your stabilizer, cyanuric acid, levels above 100 parts per million because it will stop the chlorine from working and turn your pool green." You also state that "10 ppm of cyanuric acid will protect 1.5 ppm of chlorine from UV destruction for a period of about 10-14 days with minimal outside contamination" which is complete hogwash. If you only have 10 ppm CYA in the water, 1.5 ppm FC will breakdown from the UV in sunlight quickly -- not half lost in an hour, but still cut in half in a few hours such that there is no way it will last for 10-14 days (see Table 1 in this link where the chlorine concentration is cut in half in about 3 hours at 10 ppm CYA; at 25 ppm CYA it is cut in half in around 7 hours and note that this is at pH 7 while at higher pH the loss would be faster due to more hypochlorite ion, OCl^-, that degrades faster than hypochlorous acid, HOCl). Chlorine also gets used up in other ways other than sunlight so would get to zero long before 10-14 days.

On that same Chlorine Lock page you write "it has been proven that cyanuric levels of up to 400 ppm and higher increases the disinfection powers of chlorine in swimming pool water. the reasoning is that in swimming pool water, there is the presence of ammonia which when combined with Chlorine, or cyanuric acid actually , slightly, magnifies the disinfection properties of chlorine, NOT LOWER IT, OR STOP IT." Where is the scientific evidence for this? You are right that at high CYA levels the chlorine oxidation of monochloramine takes longer so its levels can build up (to disastrous results as described in this paper), but this only occurs if there is ammonia in the pool such as from bather waste. Also, it takes much higher levels of monochloramine to be as effective as chlorine. The bottom line is that higher CYA levels reduce the active chlorine concentration to significantly slow down the killing of pathogens and the killing of algae. You shouldn't count on having ammonia in the water to form monochloramine as any sort of backup!

Since you are an NSPF CPO instructor, I suggest you read the Certified Pool Operator (CPO) training -- What is not taught thread. Note that there are many links to scientific sources that document what is really happening.

Richard

 

[chem geek]

Rob,

There's more on your website that is inaccurate. For example, in your FAQ Pool Algaecides you write that "chlorine resistant algae consume large quantities of chlorine, reducing the free chlorine available to control bacteria and viruses" as a reason why one needs to use an algaecide and cannot use chlorine alone. This simply is not true. Yes, some types of algae, such as yellow/mustard algae, require higher active chlorine levels to kill, but it is not true that chlorine alone cannot control such algae. Black algae can be similarly controlled and green algae, which is the most common, is easiest to control with chlorine alone. There are tens of thousands of members on this and other forums who maintain their pools with chlorine alone and no need for algaecides, phosphate removers, clarifiers, floculants or weekly shocking. You probably find that you need to use algaecide in your pool because you are not using the appropriate FC/CYA ratio, especially because you keep the CYA level so high in your pools.

You promote Lo-Chlor algaecide which contains copper that is chelated (complexed or sequestered), but what you need to understand is that it is only the free copper ion that kills algae and it is the free copper ion that can stain pool surfaces, especially if the pH rises. The only advantage to having the copper be complexed is that it provides a reserve for more copper rather than trying to maintain a specific copper level that may drop too quickly. This is similar to the effect of Free Chlorine (FC) and Cyanuric Acid (CYA). However, the risk of staining remains and the use of copper or any other algaecide is unnecessary if one proper maintains the appropriate FC/CYA ratio.

You promote Miraclear to prevent cloudy water, but the use of a clarifier or floculant is not normally necessary if one properly maintains their pool. Dull or cloudy water can occur from algae growth in its early stages and this is easily prevented by maintaining an appropriate FC/CYA ratio. If better filtration is desired in a sand filter, then one can Add DE to a Sand Filter.

Likewise, phosphate removers are not necessary. We have many pools on this forum, including my own, that have had very high phosphate levels (mine was recently 3000+ ppb) that have chlorine alone prevent algae growth. When the FC/CYA ratio is sufficient, algae are killed much faster than they can grow so not only is the water kept clear but there is no unusual chlorine demand either. You can read about my own personal experience with a phosphate remover and an enzyme product in this thread where there was no change in chlorine demand and the water quality didn't change (it was excellent to begin with).

The ABCs of Pool Water Chemistry has some good info including using bleach, how Trichlor and Dichlor add CYA while Cal-Hypo adds CH, how the TA should be kept lower when there are water aeration features since that tends to cause the pH to rise, etc. However, under the TA and specifically the ATA section, there is the sentence "Here at TFP you should always use the TA result directly from the test." so apparently much of this particular page was copied from TFP's ABCs of Pool Water Chemistry without attribution. You did add some items such as "10ppm of CYA will protect 1.5ppm of Cl2 from UV destructon" which is incorrect as I've noted earlier in this thread. Imitation is the sincerest form of flattery, but an attribution would be appropriate.

Richard