Ph & alkalinity Problems

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
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Ph & alkalinity Problems

Postby tigerpilot » Mon 29 Mar, 2010 14:44

South Florida
DiamondBrite Finish 18 months ago
Salt system
Water has always been crystal clear.

Here's the problem: Ph adjustment (Liquid acid) is no problem but TA is low (30 ppm) If I add Bicarb. I can bring the alkalinity up to 80 but then the Ph goes way up. I'm constantly chasing these two chemicals.
Any help is appreciated.

chem geek
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Ph & alkalinity Problems

Postby chem geek » Mon 29 Mar, 2010 17:38

Don't try and bring up the Total Alkalinity (TA) as high as 80 ppm. For a saltwater chlorine generator (SWG) pool, or any pool using a hypochlorite source of chlorine, you can have the TA be lower, even as low as 50 ppm if that's what it takes for the pH to not rise as quickly. Remember that TA is a SOURCE of rising pH itself. Higher TA does greater pH buffering so acid/base additions result in a smaller change in pH, BUT higher TA also means more carbon dioxide in the water so it outgasses faster to air and that causes the pH to rise (with no change in TA, for technical reasons I won't get into here).

If you end up with a lower TA target, then you can raise your Calcium Hardness (CH) level to compensate for the saturation index to protect your DiamondBrite finish. I would also target a pH of 7.7 instead of trying to fight keeping it at 7.5 (use The Pool Calculator to calculate the saturation index). Read Water Balance for SWGs for more tips including having a higher CYA level of around 80 ppm (with a minimum FC of 4 ppm) and using 50 ppm Borates for more pH stability.

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