TA balancing

[gilbee]

With the plaster a month old, as expected the pH is rising daily, and because of that I'm adding MA daily or every other day depending on the pH rise. As such, the TA is lowering as I add MA. I'm now down to 70. How low should I let this go before I add something to raise TA up again, and how far should I take it, assuming it's just going to lower again?

 

[Bama Rambler]

I wouldn't worry about it until it gets to about 60 or less.

 

[chem geek]

I'd keep the TA from getting any lower so that your saturation index is still close to 0 or maybe slightly higher. During curing you want more of a bicarbonate startup approach where the calcium hydroxide produced from curing (or exposed from earlier curing) gets converted to calcium carbonate. To do that, you need bicarbonate in the water, so need TA. If you need to raise it to balance the CSI, then you can go to 80 or 90. Remember that for your 17,400 gallons pool it takes 44-1/2 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid) to lower the TA by 10 ppm.

If this plaster weren't so new, I wouldn't worry about the lower TA, but given how new it is then I think it best to keep the water very saturated with calcium carbonate. See A Bicarb Start-up guide for TFP members even though you may not have started out with such a startup.

After another few months, you can consider having the TA be lower if that has the pH be more stable to minimize carbon dioxide outgassing. Also, don't try and lower the pH below 7.5. It may settle in at 7.7 or 7.8 and that may be OK.

 

[gilbee]

Bama Rambler, and then? I expect that to happen within the next week, week-and-a-half...

- - - Updated - - -

I'd keep the TA from getting any lower so that your saturation index is still close to 0 or maybe slightly higher. During curing you want more of a bicarbonate startup approach where the calcium hydroxide produced from curing (or exposed from earlier curing) gets converted to calcium carbonate. To do that, you need bicarbonate in the water, so need TA. If you need to raise it to balance the CSI, then you can go to 80 or 90. Remember that for your 17,400 gallons pool it takes 44-1/2 fluid ounces of full-strength Muriatic Acid (31.45% Hydrochloric Acid) to lower the TA by 10 ppm.

If this plaster weren't so new, I wouldn't worry about the lower TA, but given how new it is then I think it best to keep the water very saturated with calcium carbonate. See A Bicarb Start-up guide for TFP members even though you may not have started out with such a startup.

Maybe I'm being too aggressive with my approach...when I see the pH rise above 7.8, I target to lower it to 7.0-7.2, then let it rise again...I have added at least 5 gallons of 31% MA since I've started this, I don't recall what the plaster company added during their startup, but I'm fairly religious about keeping the pH in the right range and pushing it down to low 7 when it's not. Should I stop pushing down to 7.0 and use smaller dosages to maybe never dose to be below 7.4?

 

[chem geek]

Yes, you are essentially doing a "lowering TA procedure" by going so low in pH. Don't do that. Use smaller dosages to just get down to around 7.5. I'll bet you will be using a lot less acid over time even though you will still be adding it frequently. Your TA will drop more slowly as well.