Interesting article on CYA

[newfool]

Hello all, I was reading an interesting article on CYA. I have been watching my level go up now for the last several weeks. I was concerned because trichlor pucks are the main cl source for my pool and I know that once its in, its there for good!

I especially liked the author pointing out the fact that cya is most effective at such a low level - way below 100 - read on to find out :-D



http://www.ppoa.org/pdfs/PrP_Cyanurics - Benefactor or Bomb.pdf

 

[JasonLion]

That article is an interesting mixture of exactly right, somewhat misleading, and dead wrong. In particular, their chlorine "staying power" graph is wrong. Higher levels of CYA continue to reduce chlorine loss to sunlight significantly, much more than their graph shows. Their bug-killing-power chart is misleading because you should be raising the FC level at higher CYA levels, which will restore the kill times observed at lower CYA levels. At the same time, their pushing people to be more aware of their CYA levels is very appropriate.

 

[meatloaf]

Rising CYA levels is a problem when using the "pucks" to chlorinate a pool. I've for one have often wondered why manufactures can't cut back on the amount of stabilizer in the puck, or manufacture pucks with different amounts of stabilizer. :?

 

[JasonLion]

Chlorine is very volatile and sometimes poisonous. There are only a couple of chemical compounds which are reasonably safe to handle and which release active disinfecting chlorine when dissolved in water. Two of them, dichlor and trichlor, contain CYA in specific ratios to chlorine. They could add more CYA to the tablets, but not less. Any less CYA and it wouldn't be safe and stable any more.

 

[meatloaf]

Thanks for the explanation.

 

[yitbos1]

I would like to have the gurus here respond to one sentence in particular:

"...as CYA exceeds 70 ppm, virtually any level of chlorine will result in no more than about .2 ppm equivalent effectiveness."

Figure 1 shows this graphically as the lines of FC converging at 70 ppm CYA. Therefore, regardless if I have 1 ppm FC or 20 ppm, there will be the same effective level of chlorine when at a CYA of 70 ppm. From what I have read here over and over, this does not seem to be true. Thoughts?

 

[JasonLion]

"...as CYA exceeds 70 ppm, virtually any level of chlorine will result in no more than about .2 ppm equivalent effectiveness."

That is simply false. There is a chart here, where you can see the correct relationship. With CYA of 100 you need a FC level of about 20 to be equivalent to no CYA and 0.2 FC. FC above 20 gives you higher effective FC levels (actually HOCl levels).

You need significantly higher FC levels to get the same effect at higher CYA levels, but it can be done straightforwardly.

 

[Guest]

While the author of the article, Kent Williams, does make some good points, such as high TDS not being a problem but rather high CYA levels (which will go hand in hand with high TDS in pools chlorinated exclusively with stabilized chlorine sources) causing problems (because the FC is too low for the CYA level) but the focus of the article is on pools controlled with ORP controllers (which do not operate properly when there is CYA in the water!), which is not surprising since he was formerly employed by Stranco (a major manufacturer of ORP controllers) before he started PPOA. Therefore his article could hardly be called objective. I find it very interesting that he says at the end of the article:

"This writer has, by the way, used cyanuric acid successfully
and with benefit in his own pool for years."

Here is an article Stranco wrote on CYA:
http://www.strancoaquatics.com/lit_f...ilization1.pdf
It is basically more of the same.