CDC stated to avoid eye irritation to keep PH at 7.3

benavidescj

LifeTime Supporter
Apr 27, 2010
431
Fleming Island, FL
Split off of this topic. JasonLion

I was reading a CDC article that stated that to avoid eye irritation to keep the pH at 7.3. None of the recommended pH levels at TFP go that low. I am not real sure how sensative eyes are to pH levels above 7.3 (like 7.5 - 7.8), but it may be the cause of irritation. I would like to know myself because your levels look good to me and my kids suffer with red eyes as well.
 

benavidescj

LifeTime Supporter
Apr 27, 2010
431
Fleming Island, FL
Re: Red eyes!?!?

Just noticed a post where Jason stated that the CDC recommendation of pH 7.3 is only valid at a CYA level of 0. Don't know how CYA affects this but maybe Jason can explain. We might be floating towards the Deep End.
 

JasonLion

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May 7, 2007
37,880
Silver Spring, MD
When there isn't any CYA in the water (and only then) the effectiveness of chlorine varies dramatically with the PH. Without CYA, PH around 7.8 results in dramatically lower effective sanitizer levels than PH around 7.3. From a purely chlorine effectiveness point of view you would actually want the PH even lower, but PH below 7.2 causes other problems, so they recommend PH around 7.3. If the chlorine is not effective enough, there can be things (bacteria, CC) in the water which will cause eye irritation.

As soon as you add CYA, the relationship between PH and chlorine effectiveness changes significantly, becoming a relatively minor factor that can be ignored most of the time.

In the topic where this first came up, FC/TC testing errors are presumably hiding a CC above 0.5 problem.
 

chem geek

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Mar 28, 2007
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San Rafael, CA USA
This post gives more info on the pH of human tears (averages 7.5) and on eye irritation (not usually caused by pH in the 7-9 range; mostly due to chloramines or to lower salt levels resulting in greater osmotic pressure).