TA opposed to PH
by Bill Pike
(Virginia Beach, VA USA)
Commercial pool total alkalinity vs. pool pH level...
I operate several pools both indoor and outdoor. I have one outdoor pool that I have been having an ongoing issue with.
The pH stays high 7.8 - 7.9 while the total alkalinity is low 30 - 40 ppm. Anything I do to try to raise the TA of course raises the PH, any advise?
The pool is a commercial (hotel) at 90,000 gallons the current temp is around 77. The later Summer temps will be up around 80 - 87.Thanks for your questions Bill
The YMCA pool is 80,000 gallons so we're pretty close to your commercial pool. The pH level of our fill water runs 8.0ppm and the total alkalinity is 30ppm so I have the same issue as you.
Hopefully you are using a Reagent FAS-DPD K-2005or 2006 test kit.
First you'll want to lower the pool pH level. I found that 1 gallon of acid reduces the Y's pool by 0.2ppm. You may want to use 1 1/2 gallons, but there's a way you need to do it so it won't affect the alkalinity too much.
You can go to this link and find exactly how I do it.
The short of it is to put the acid around the perimeter of the pool starting at the deep-end and the filtration running. If you have any water features you need to turn them on to help with aeration. Keep the water moving when decreasing a pool's pH level.
Wait for one complete turn-over of the water. Usually state law requires a complete turn-over every 6 - 8 hours with about 240 - 280 gallons per minute (GPM).
Once the pH level is around 7.2ppm it's time to raise the total alkalinity. I have always used sodium bicarbonate and it works very well.
Turn the filtration off and put the bicarb in one place in the deep-end. With the Y's pool it takes about 200oz. of bicarb to raise the alkalinity 10ppm.
Allow this to sit for 2 - 3 hours, turn the pump filter back on, and wait for 1 complete turn-over.
Re-test the pH and alkalinity and make another adjustment.
Keep testing and going back and forth with the pH and TA until you reach your goal of 7.6 - 7.8ppm for the pool pH level and 80 - 100ppm for the total alkalinity.
This works for me every time.
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