Lowering TA Frustration

[Miranda]

I just refilled my pool (recent liner change) and am beginning the arduous process of lowering the TA (My fill water is 220-230) and pH drifts up unless I get the TA down. I have done this before using the aeration method with success but this time it isn't going so well. The problem is getting the pH down to begin with. After 24 hours of adding acid a quart at a time, waiting 30 minutes, testing then repeating the pH is still hovering around 7.3-7.5 at its lowest. This after TEN qts of MA total have been added to a 26500 gal pool. I tried aerating overnight even though the pH wasn't down much, but ended up at pH 8.0 in the morning with NO change in TA.

Any tips? Should I continue to add acid aiming for 7.0 then aerate to 7.6? Or just work with the higher pH I've got and aerate from 7.5 to 8.0, then repeat?

By the way, I use the BBB method, but have not added any liquid chlorine yet. I am chlorinating with trichlor shock for now in order to help lower pH and add some CYA.

Current test results/appearance: CL 3.0, pH 7.4, TA 220, CH 50, CYA trace, Borates 0 (will add later). I used softened water (house water softener) for fill due to very high iron content (Have done this before without issue, no need for hardness in above ground vinyl pool). Water started off a little green due to remaining iron content, but iron has since filtered out, backwashed and water now looks beautiful, and clear. PH drift due to high TA is only issue.

 

[Bama Rambler]

According to pool calc it will take 1½ gallons to lower the pH from 7.6 to 7.0. And almost 3 gallons to lower it from 8.0 to 7.0. Your high TA puts upward pressure on the pH so it takes a lot of MA to lower it very much at all

 

[Miranda]

Yes, I see that now. I had forgotten to hit calculate after inputting the TA, so I was getting 91 oz needed. Still, I have put in quite a bit more than that. I finally hit 7.1, after dumping in an OLD 1/2 bottle of acid that had been sitting around for months. I wonder if the newer acid I bought was bad? I decided to go with that and turned on the aerator and went to bed. We will see what we have in the morning.

I am wondering if I should just aerate first, drive the ph WAY up then bring it down, sortof in reverse order?

 

[Bama Rambler]

Either way works just be sure not to get too far out each end of the scale.

 

[Richard320]

I am wondering if I should just aerate first, drive the ph WAY up then bring it down, sortof in reverse order?

Plug some numbers into pool calculator. You'll see that pH is a major factor in CSI. You don't want scaling or etching. Or dissolving copper from the heater into the water.

If you scroll way down the page on pool calculator, you'll see where adding 128 oz (1 US gallon) of acid will lower your pH by .12 and TA by 18. It will take a while - and a lot of acid - to get TA down. You just have to be patient.

Add acid to get pH to 7.2, aerate and retest. I have a spa, so if I am in a hurry, I divert all the return to it and have lowered TA 30 ppm in 5 hours before. You probably don't have that luxury. So get the surface churning; point the returns up, devise an aerator to go on the return, something! Do a search on aeration. Or aerator.

I wouldn't recommend trying to get TA in line in one shot.

 

[Miranda]

Success!! I got up a couple times during the night and added more acid, go the pH down to 7.0 and turned on the fountain. Total acid 5 gallons so far. This morning ph had gone back up to 7.5 and the TA is at 150. That is 80 points from where I started! I want to keep going to 70 since I will be using liquid chlorine and adding borates.

Richard, what is CSI? I have an aboveground pool, so is scaling and etching a concern? I don't have a heater. I have a fabulous PVC "Model T" redneck fountain that laughs at spa jets.

 

[chem geek]

If you have a vinyl pool and no exposed grout in tile touching the pool water, then don't worry about the Calcite Saturation Index (CSI) unless it remained high. If you had plaster or other similar surfaces that needed saturation of the water with calcium carbonate, then after lowering the TA you could raise the CH level to compensate, but that doesn't sound like your situation.

 

[Richard320]

Richard, what is CSI? I have an aboveground pool, so is scaling and etching a concern? I don't have a heater. I have a fabulous PVC "Model T" redneck fountain that laughs at spa jets.

In simple terms, how much calcium the water can hold before it starts leaving it places. A positive number means scaling - it has more Calcium than it can hold. Negative means it will leach it out of things. If you have nothing metallic or cementish (is that a word? grout, mortar, plaster) in contact with the water, it's not a worry.

 

[Miranda]

Ah...thanks, I don't have anything to leach from, so I'm good there.