low TA high PH...... should I be concerned?

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
youngskywalker
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low TA high PH...... should I be concerned?

Postby youngskywalker » Wed 06 Jul, 2016 21:32

10,000 gal cement plaster pool with Spa spill over. Salt water chlorine generator. Taylor 2006 test kit, plus others.

CH 375
Chlorine 3
Borate 40
Conditioner 65
Salt 3300
PH 7.8
TA 40
Phosphates 700

Pool looks and feels great! Water clarity is perfect 95% of the time. Algae problems are few and far between. Question is, should I be concerned about my TA level? Everyone suggest 80-120. Mine drifts between 40-50. Maybe even as low as 30 on a bad day!

My PH starts to stabilize around 7.8 So I keep it in the range of 7.6-7.8 by adding a small dose of muriatic acid about once every 2 weeks. I don't worry about it too much.... just keeping it at the high end where it likes to be.

But what about my TA? I've tried to fight it by adding baking soda but that is honestly useless. Yes, it does raise TA for a few days but then right back down it goes. I also try to turn off my overflow from the spa at least half the day. I know that effects PH and TA but I still need to circulate some water so shutting that off more is out of the question.

So, what do you think? Fix it or let it be? Is TA of 30-50 O.K.?


chem geek
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Re: low TA high PH...... should I be concerned?

Postby chem geek » Thu 07 Jul, 2016 03:30

The TA would only fall back down if you were adding acid to lower the pH. You can operate at a lower TA if the pH is stable and maintained in the range you have, but because of your plaster pool surface you would need to have the Calcium Hardness significantly higher especially with the higher salt level in a saltwater chlorine generator pool. If you put your numbers into PoolMath assuming 85ºF water temperature you get a Calcite Saturation Index of -0.75 which is quite low and would tend to dissolve plaster. While you can target something slightly negative such as -0.2, that would mean raising the TA to around 60 ppm or the CH to 1200. Since it's much easier to control the TA than diluting the water to lower the CH, I suggest you raise your TA to 60 ppm and see how much acid you need to keep the pH in the 7.6 to 7.8 range. If you really think you need your TA lower, then consider raising the CH.
youngskywalker
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Joined: Wed 06 Jul, 2016 20:29
My Pool: 10,000 gal

Re: low TA high PH...... should I be concerned?

Postby youngskywalker » Thu 07 Jul, 2016 19:23

I think I can keep my TA around 60 if I hold my PH around 7.8. Although it may rise to 7.9 or 8.0 between additions of acid. It rises, slowly. I only have time to add acid 2 times per week.

Bottom line is I think I will target 7.8 and let it be.

Adding 4 times the amount of calcium is not the road I want to go down. If I had problems with the pool I would try anything but like I said. Water quality is good with almost no problems. Even the plaster seems to be doing very well. I do have minimal scale deposits if that helps in your assessment.
chem geek
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Re: low TA high PH...... should I be concerned?

Postby chem geek » Sat 09 Jul, 2016 03:40

You shouldn't be getting any scale with your low CSI unless it's only in an area of evaporation like on the side of a waterfall.

You can do what you wrote. The only downside to the higher pH target would be metal staining if you had metals in the water (e.g. dissolved iron, copper, manganese).
youngskywalker
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My Pool: 10,000 gal

Re: low TA high PH...... should I be concerned?

Postby youngskywalker » Sat 09 Jul, 2016 19:16

It's just like you said, the only scale is at the waterfall. Rest of the pool is clean as a whistle.

There is zero metal staining. So I think I'm going to run it like it is. If problems arise then I'll address them when the time comes. Thanks for the help.
youngskywalker
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Joined: Wed 06 Jul, 2016 20:29
My Pool: 10,000 gal

Re: low TA high PH...... should I be concerned?

Postby youngskywalker » Wed 13 Jul, 2016 19:48

I let it ride this last week. TA is 40 and PH stabilized at 7.7

I did however notice that the water didn't have the nice soft feel that I desire. My Chlorine also spiked to 4.2 so maybe that has something to do with the feel of the water (which is a simple adjustment on my generator).

My question is, if I did continually add baking soda and acid will there be a buildup of anything undesirable over time???
chem geek
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Re: low TA high PH...... should I be concerned?

Postby chem geek » Sun 17 Jul, 2016 01:38

As I wrote before your CSI is very low and with a plaster/cement pool that means that material may slowly dissolve in that water. If you want to keep your TA that low you'd need to have your CH higher to compensate.

As for your chlorine, with your CYA level you could target around 3 to 3.5 ppm FC.

The combination of baking soda and hydrochloric acid is identical to adding carbon dioxide and salt. So the buildup will be sodium chloride salt. To get out of the bicarb/acid cycle you shouldn't try raising the TA as much and you can keep the pH higher. That is what you are doing now except your CSI is still too low to protect plaster/cement surfaces.

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