PH just keeps going up!!!

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
rustyswim
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PH just keeps going up!!!

Postby rustyswim » Wed 05 Aug, 2009 19:17

I run a 120,000 gallon pool with drop slides and playground features that runs to zero depth. I am awlays at a reading of 8 or greater for my pH. I add so much dry acid at night but it goes down only for a few hours. I once added 50lbs. of dry acid to see if it would stay down. It went to 7.2 for 3 hours and then went right back up. I know to add acid slowly and over time, but this is going on a few months. WTF!!!


chem geek
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PH just keeps going up!!!

Postby chem geek » Thu 06 Aug, 2009 22:09

You have a lot of aeration in the pool you run and this outgasses carbon dioxide which causes the pH to rise. This will occur more quickly when the Total Alkalinity (TA) is higher. Ironically, having the TA lower will reduce this rate of pH rise. You'll need to compensate for the lower TA with a higher Calcium Hardness (CH) to protect plaster and keep the saturation index near zero. You can also target a higher pH of around 7.7 since the carbon dioxide outgasses more slowly at higher pH.

What is your current TA? Unless you are using an acidic source of chlorine, you could go as low as 50 ppm in TA (if the CYA isn't higher than 30 ppm). What is your source of chlorine? Is it hypochlorite of some sort -- sodium hypochlorite perhaps?
RMS1
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PH just keeps going up!!!

Postby RMS1 » Sat 15 Aug, 2009 10:59

rustyswim wrote:I run a 120,000 gallon pool with drop slides and playground features that runs to zero depth. I am awlays at a reading of 8 or greater for my pH. I add so much dry acid at night but it goes down only for a few hours. I once added 50lbs. of dry acid to see if it would stay down. It went to 7.2 for 3 hours and then went right back up. I know to add acid slowly and over time, but this is going on a few months. WTF!!!


Check geek is right. Check to make sure the alkalinity of between 80-100. Outside pool check for cyanuric acid, indoor pool, don't worry about it. I have an 80,000 YMCA pool I take care of and we don't have this problem.

It also depends on how many swimmers you have. More swimmers will raise the pH. Be sure your chlorine is 3.5-4.5, alk. 80-100, ph 7.6-7.8, and hardness 150-250.
rustyswim
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PH just keeps going up!!!

Postby rustyswim » Tue 18 Aug, 2009 17:51

We are using Cal Hypo to chlorinate currently, had issues with chlorine hoses. Currently we have had trouble getting the TA down as well. It is at 100ppm. I know that is within range but if I should go lower to stop the pH from creeping up, I will. But I have been dumping a lot of Dry Acid and this is not really helping the TA. Our Calcium Hardness was right in range as well. Let me know what you think.
chem geek
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PH just keeps going up!!!

Postby chem geek » Tue 18 Aug, 2009 22:59

If you keep adding acid then it doesn't make sense for the TA to not drop unless it is getting added elsewhere. Measure the TA (and CH, for that matter) of your fill water. If you've got a lot of evaporation and refill, which you probably do with water slides, then whatever TA is in the fill water will get added to your pool (the same is true for CH). I assume you haven't been adding any pH Up (soda ash / sodium carbonate) or Alkalinity Up (baking soda / sodium bicarbonate).

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