Question
Asked 3rd Feb, 2013

Optimal pH in swimming pools

In Denmark it has been discussed in the last about 5 years if reducing the pH in swimming pools below the traditional range of 7.2-8.0 can improve the chlorination by-products profile. Some studies including our own results suggests that THM and combined chlorine (chloramines) decreases if the pH is maintained below 7.0, but our own results show an increased formation of the geno-toxic haloacetonitriles (HANs) and we could also confirm old literature reports that trichloramine formation increases drastically at pH below 7.0.
We have learned that the recommendations and/or regulations for pH in chlorinated swimming pools vary considerable between countries. Can anybody tell that the regulations are in different countries and most interestingly if they know that the basis of the regulation is?

Most recent answer

7th Jun, 2015
Randa M. Osman
National Research Center, Egypt
thank you for all
very useful discussion
best regards
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Popular Answers (1)

24th Feb, 2013
Muhammad Saqib Khan
COMSATS University Islamabad
Hi Henrik
The pH value and the concentration of the disinfectant in the water are important parameters. In Malaysia, the pH value should be maintained between 7.0 and 7.2 according to the regulations set by central government.
while I was reading a US guidelines for swimming pools, its stats that the chemical quality of the water shall be maintained in an alkaline condition at all times with the pH between 7.2 and 7.8.
5 Recommendations

All Answers (17)

24th Feb, 2013
Muhammad Saqib Khan
COMSATS University Islamabad
Hi Henrik
The pH value and the concentration of the disinfectant in the water are important parameters. In Malaysia, the pH value should be maintained between 7.0 and 7.2 according to the regulations set by central government.
while I was reading a US guidelines for swimming pools, its stats that the chemical quality of the water shall be maintained in an alkaline condition at all times with the pH between 7.2 and 7.8.
5 Recommendations
24th Feb, 2013
Henrik Rasmus Andersen
Technical University of Denmark
Hi Muhammad,
It sounds like Malaysia already have made a very good choice for pH in swimming pools.
My group is just about to submit a follow up study of the effect of pH in swimming pools for disinfection byproducts formation to a scientific journal. We conclude that the optimal value for pH is as narrow as 7.0 to 7.2, exactly as you already have in your regulation.
2 Recommendations
24th Feb, 2013
Muhammad Saqib Khan
COMSATS University Islamabad
That sounds good, shall be waiting for the article to come online, am interested to read your findings...:)
Actually in Malaysia, skin diseases are more common and what I think these may due to high humidity, even, we cannot wear clothes if hanged for a week inside, this cause skin infections, I am not sure about the municipal water supply pH regulations (need to check), so I think there may be some connection between the skin infection and pH, may be or may not be...:)
2 Recommendations
29th Mar, 2013
Henrik Rasmus Andersen
Technical University of Denmark
The paper will most likely take many months. I just remembered that we have a poster online with some of the data about finding the optimal pH for pool water for minimizing the disinfection by-products.
2nd May, 2013
Maarten G.A. Keuten
Delft University of Technology
In the Netherlands, the current regulations allow a pH window between 6.8 and 7.8. The Dutch regulation for swimming pools is now being renewed. For the new legislation, the pH window is suggested between 7.0 and 7.6. This new legislation is planned to come into effect in 2015.
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7th May, 2013
Davide Papurello
Politecnico di Torino--Energy Center
Free available chlorine residual, total chlorine residual, pH, total alkalinity, and calcium hardness are perhaps the five most critical pool water care factors that, if not managed properly, can lead to pool water chemistry problems.
Considering pH experts generally agree on a pH that ranges from 7.4 to 7.6.
10th May, 2013
Kaveh Kheirkhah Rahimabad
Islamic Azad University Tehran Science and Research Branch
Hi!
the pH of most in swimming pools in Iran about 7.2 to 7.6 ... this standard sent from Iranian Environmental Health Organisation (every year). High pH can also create problems of its own. When pH values climb too high (7.8 and up), the pool water has a tendency to look dull or flat. High pH can also cause skin and eye irritation. When the pH rises, the sanitizer becomes less effective. This means the pool will require more sanitizer to keep it clean.The pH of pool water has a great effect on how comfortable it is for swimmers. Your eyes have a pH of about 7.3 to 7.5. As mentioned above, when pH strays too far away from this point, pool water becomes increasingly uncomfortable. Red, irritated eyes are an indication that the pH might be out of balance and should be checked.Taking all this into consideration, you will best meet your objective by keeping the pH between 7.2 and 7.6. This range combines the maximum swimmer comfort with sanitizer effectiveness.
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28th Jul, 2013
Henrik Rasmus Andersen
Technical University of Denmark
It seems that most of you have quite reasonable pH values in your national regulations.
Our paper is finally published and it agrees with Maartens information on the Dutch new standard that pH should not be below 7.0.
27th Aug, 2013
Henrik Rasmus Andersen
Technical University of Denmark
I found a description of a suggestion to run pools at pH around 8.0. They promise a explanation in a paper that will come later. Does anybody know about this idea or have comments?
29th Aug, 2013
Rolf Frankenbach
Humboldt State University
Another aspect of pool pH to consider is that low pH causes pool water to be "agressive" and dissolve metals and plaster surfaces, whereas high pH causes water to "scale" or deposit calcium carborate on pool surfaces making them feel rough to the touch and more likely abrade skin. So, maintaining a moderate pH avoids these extremes.
1 Recommendation
30th Aug, 2013
Boris Kompare
University of Ljubljana
Dear all! My comment - or question ... if we leave aside the legal limits for the pH of swimming water, which pH is more comfortable for swimming? My personal experience is slightly alkaline is better than neutral which is again better than slightly acid.
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31st Aug, 2013
Henrik Rasmus Andersen
Technical University of Denmark
The factors Rolf mention together with the formation of the very irritating and volatile, trichloramin, at pH lower than about 7 have been the reason for keeping pH around 7.4 up to 8.5 earlier.
I believe the reason it is discussed in technical circles to change pH in pools is the that the materials used in swimming pools have changed:
* Metal parts are often a higher grade of stainless steel that can tolerate low pH and high chloride concentrations.
* The pipes in the system are PVC or other polymer materials that don't corrode at all.
*The mortar in grit and glue for the tiles can be very pH resistant 2-component products.
* Some pools even use ion exchange to soften the fill water to prevent scaling in membrane or other very tight filters. Therefore we can technically choose to operate at high pH without scaling problems and low pH without corrosion.
2 Recommendations
31st Aug, 2013
Henrik Rasmus Andersen
Technical University of Denmark
I find water at about pH 6.5 more pleasing. It appears almost tasteless or slightly sweet to me.
As soon chloramines are present in the water the water is much better at pH around 7.5.
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7th Sep, 2013
Hooshyar Hossini
Kermanshah University of Medical Sciences
i think there is your answer in ENVIRONMENTAL ENGINEERING Published by John Wiley & Sons, Inc., Hoboken, New Jersey Published simultaneously in Canada JOSEPH A. SALVATO, P.E., DEE Copyright  2003 part 9 9 Recreational Areas and Temporary Residences
15th Jun, 2014
Lala Behari Sukla
Siksha O Anusandhan University
You should aim for a pH level of between 7 and 7.6. If the water pH is higher than 8, anyone who swims in the pool is at risk of skin rashes, while a pH of lower than 7 can sting the swimmers' eyes.Some of the many factors that can affect your pool's pH level include heavy rain, lots of swimmers and pool chemicals. Remember to regularly check your pool's pH level.http://www.betterhealth.vic.gov.au/bhcv2/bhcarticles.nsf/pages/Swimming_pools_water_quality
4 Recommendations
11th Dec, 2014
Henrik Rasmus Andersen
Technical University of Denmark
If anybody are still following this question they might find this modeling paper conclusion about the effect of pH in the pool interesting:
"Thus, the model indicates that the decrease of pH from 7.25 to 7 contributes to a significant increase of NCl3 formation i.e. about 40% with the same experimental conditions in the investigated pool."
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