Mike the Poolman


Is pH 8.0 to 8.5 Okay for Swimming Pools?

January 23, 2020

Reprinted with permission from onBalance January 2020www.poolhelp.com

There should NOT be a mandate to close down swimming pools when the pH is 8.0 to 8.5.

Obviously, it is important to ensure that pool water is safe for swimmers, but some standards are too restrictive, and the pH range is one of them.

Starting sixty years ago, pool industry chemists (incorrectly) suggested that a pH of 8.0 and higher makes chlorine ineffective and not safe to swim in. But the truth is that just 1 ppm of chlorine in pool water with a pH of 8.5 and zero CYA contains more active chlorine (HOCl) than needed to kill algae.

Today, thanks to several chemists, it is now understood that CYA, not pH, is what significantly affects chlorine efficacy. But some industry people seem to be misinterpreting or not understanding that science. Some still seem to think that when pool water contains CYA, a pH above 7.8 significantly prevents chlorine from sanitizing, and that raising the chlorine level will not help improve sanitizing effectiveness. That is false.

One way to explain this is to consider that water with 3 ppm of chlorine at pH 8.5 has more killing power than 2 ppm of chlorine at pH 7.5 when both contain 50 ppm of CYA. Plus, there is 1 ppm extra of chlorine in reserve if needed. That should help illustrate that a pH above 7.8 does not prevent chlorine from properly sanitizing pool water.

Now, back to the issue of the industry’s mandate to close pools when the pH is above 7.8. Why? We know that the maximum pH 7.8 level was based on incorrect science and assumptions. The pH range of 7.2 to 7.8 should be considered an IDEAL range, not the minimum and maximum. Many pool service companies have been successfully maintaining the pH between 7.8 and 8.2 on tens of thousands of pools without reports of disease or algae outbreaks resulting from high pH. And there is a peer-reviewed study showing that lowering the pH from 8.0 to 7.0 increased the frequency of eye irritation.

Furthermore, some tap water, serving millions of people, has pH levels above 8.0 and up to 9.3. The always restrictive EPA allows a pH up to 8.5 for drinking water.

It is known that the (natural) pH of water containing carbonate alkalinity of at least 60 ppm will want to rise to 8.0 – 8.2 and may go as high as 8.5 if the alkalinity is above 140 ppm. If the LSI is within the balanced range, why fight that tendency and constantly add acid and then sodium bicarbonate to replace the lost alkalinity? Why restrict those who have experienced success and prefer the ease and increased stability of maintaining a higher pH level? 

Why sound a false alarm to pool owners that their pool water is out-of-balance and unsafe when it is not? That simply undermines service techs unfairly. 

Dr. Stan Pickens has written a scientific report on this topic which can be viewed by clicking on this link.  http://www.poolhelp.com/wp-content/uploads/2019/03/JSPSI-Volume-6-Number-1-pp-06-19-Pickins.pdf

(reprinted with permission from PoolHelp.com/ onBalance January 2020) www.poolhelp.com

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