Cannot lower TA to 100 after aeration

[GreenOak]

My TA was high in April--around 200. From reading the aeration instructions here, I've been adding muratic acid first, then sodium bisulfate, since 4/27 I believe. By May 1, my TA readings were averaging around 130. Since then, I have still been aerating 20-24 hours a day and have added almost 20 lbs of bisulfate daily or every other day when pH gets to 7.2 to 7.4. During this entire span, I have successfully lowered pH to 7.0 or less with each treatment, but have not been able to get TA to go any lower on average, as I still read 130.

When I say average, that is a result of several test strip readings. While strips may not be the most precise method of testing, they do seem to be detecting the fluctuations in pH in the manner expected with each treatment.

So is it possible that there is something about the water that keeps this level as a floor, such that I should just stop trying to lower it to 100 and leave it as is? The only thing that looks suspicious is a correlation that when using muratic acid in April I had success, but since switching to powder I have not.

 

[frustratedpoolmom]

We don't recommend powder. Stick with the muratic acid.

Do you have an autofill? No water has been added to the pool during this time?

 

[JasonLion]

Welcome to TFP!

Lowering TA does take quite a while. However, your fill water TA level might be fairly high. If so, and if you have been adding water to the pool, that might be keeping the TA level up.

You could also be having problems with the test strips. Just because the PH reading has been making sense, doesn't mean that the TA reading is correct. Also, the results from test strips lack precision, so you might simply not be able to detect the color change from TA going down slowly.

 

[GreenOak]

We don't recommend powder. Stick with the muratic acid.

Do you have an autofill? No water has been added to the pool during this time?

Yes, there is an autofill, but it was not active. It did just rain on May 8, 9, and 12. 4" in fact on the 12th. Less than 1" the prior week. But the TA seemed stable even before it rained for about a week.

Your suggestion about acid is interesting. Is it a known issue that powder is not effective for lowering TA?

 

[GreenOak]

Welcome to TFP!

Lowering TA does take quite a while. However, your fill water TA level might be fairly high. If so, and if you have been adding water to the pool, that might be keeping the TA level up.

You could also be having problems with the test strips. Just because the PH reading has been making sense, doesn't mean that the TA reading is correct. Also, the results from test strips lack precision, so you might simply not be able to detect the color change from TA going down slowly.

Thanks Jason. True about the TA strip measurement not being correct. As I mentioned in the other reply, I don't believe the level was low enough to trigger the autofill. Rain did not appear to elevate the TA in any noticeable way, but there definitely won't be any more autofilling since it is now dumping after the downpour.

I had three readings this morning of 130. I wonder if I should just accept this level. BTW, there is no SWG.

 

[Richard320]

Yes, there is an autofill, but it was not active. It did just rain on May 8, 9, and 12. 4" in fact on the 12th. Less than 1" the prior week. But the TA seemed stable even before it rained for about a week.

Your suggestion about acid is interesting. Is it a known issue that powder is not effective for lowering TA?

Acid is acid. Anything that lowers pH will also lower TA. Muriatic acid is cheap, and when it breaks down, it's just hydrogen and chlorine.

Dry acid is Sodium bisulfate. I don't know what it breaks down into, do you? I do know their's sulfur in there, and sulfur stinks. What conditions might cause it to form smelly compounds? I don't know, and I don't want to find out! Once you pour something into your pool, it mostly stays there. I know some things break down into CO₂ and just blow away, some turns into salt. What does the sulfur do? Again.... I don't know, and I don't want to find out. That's why I stick to Muriatic acid.

Have you done a search for aerators? Some people here have built some pretty impressive devices out of PVC pipe and really gotten the surface of the pool churning. I know that with my spa on full tilt, I can lose 30 ppm TA in a few hours.

 

[DFW]

I think (based on wine making experience, never used it in my pool and prefer potassium metabisuphite) that sodium bisulfite breaks down into sulpher dioxide (rotten egg smell) and will normally gas off overtime (sometimes requires aeration or binding to copper to remove excess levels).

 

[GreenOak]

Fortunately, after adding all that powder, there is no sulphur odor. I need to go to HD--I see they carry muriatic acid. Frankly, I was a bit put off by the hazard and fumes, especially off just a small breeze, but I think I will try that again.

To Richard's point about aeration, I have several PVC fountains spraying into/across the water, but I only seem to getting maybe .4 pH rise per day, so losing 30 ppm TA seems quite impressive, and needless to say less costly.

 

[GreenOak]

I find this hard to believe, but one day after switching back to acid for one application, I have gotten TA to around 100-110. After two weeks of being stuck around 130 while using all that powder, I finally feel a great deal of relief that this is over. I wonder if I am the only person to have an experience like this, but at this point I'll be sticking to the acid.

 

[Surf Hawk]

That is great news. I have been working for a few months to bring my TA down from 200 and am kind of stuck at 130 also. I only try about every two weeks when my pH creeps up, I dose it with 1/2 to 2/3 a gallon of MA and then try to aerate when I add my fill water (hose with sprayer attached injecting air hopefully). Maybe my fill water has high TA, or maybe I never really aerate it enough to bring pH up, it just comes up slowly as it normally would.

 

[GreenOak]

That is great news. I have been working for a few months to bring my TA down from 200 and am kind of stuck at 130 also. I only try about every two weeks when my pH creeps up, I dose it with 1/2 to 2/3 a gallon of MA and then try to aerate when I add my fill water (hose with sprayer attached injecting air hopefully). Maybe my fill water has high TA, or maybe I never really aerate it enough to bring pH up, it just comes up slowly as it normally would.

I had been running the pump all day to aerate and get it over with, and tested the water twice a day at first, then once a day after discovering the rate of increase. I replaced my jets with these fountains to create bubbles on the surface. They definitely raised pH, though perhaps not as fast as some homemade solutions. Given how much time it took each day for these to have a measurable impact on pH, it may be more effective than relying on the limited amount of time you might use a hose to add water.

 

[Surf Hawk]

That is what I need to do. I have a very old pool, the return lines look like 3/4" pipe with no threads or eyes or anything.