Tough TA

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E

edison

0
Mar 10, 2009
13
Florida USA
I left my water feature on (over spill spa, 3 Jandy jet, and 3 tier water fountain, compressor )all night and guess what? TA didn't even budge :( . Stayed at 90.
pH 7.2, borax (awaiting test strip), CL 6ppm (just schocked the pool), CYA around 60.

Any other idea?
 
The TA really shouldn't be affected by the activity of your water features. On the other hand, your pH would be where you might notice the difference, this being a rise in pH due to the outgassing of CO2 from the bubbling effect of your water features. But, I'm guessing that you added borates to your pool since you indicated that you are waiting on the test strips to arrive. If you do have borates in your pool, you essentially have a second buffer system in place in your pool water now. This will blunt the effect of the pH swings in addition to your primary buffering system which is your TA. With both of those in place, you should be able to run your water features without much of a fear of a pH rise like you did before you added the borates.

Lowering the TA can take a while. It can sometimes take several days to do it and with borates in the pool, it makes it even more of a challenge. You are right on the cusp of being in range for your SWG pool since you only need to get to 80. But it may take several days to get it down where it stays down. In the end, it is always best to get your TA correct prior to adding borates since doing so afterward is so tough.
 
The waterfall will raise PH not lower TA. You need acid to lower the TA. However, because you have a low PH already, you need to raise the PH first with aeration. It could be that the waterfall isn't very effective at raising the PH. You might try another method.

Here is how the steps should work.

Aerate to get PH up
Add acid to lower TA and PH
Aerate to get PH up (TA stays low)
.
.
.

Repeat as necessary
 
Hmmm........ I'm referring to this post by chem geek

There isn't a simple chemical to add to lower the TA. The only thing that would do that would precipitate out carbonates and would then need to be scooped out, but I'm not aware of any such product (other than those that would cause staining like copper or that would cause scaling like excess calcium). Aeration to drive carbon dioxide out of the pool is the way to lower the TA. For greater aeration, using an air compressor with a nozzle or pipe with small holes to make small bubbles has been most effective, but the jet air fitting referred to in previous posts sounds like it might work well. I just bought one and will try it out this summer (my TA only needs to be lowered a little -- from around 130 to 80).

Richard
Click to expand...
 
Aeration is the critical step, but it is actually the acid which lowers the TA. We tend to focus on the aeration because there are several other "procedures" for lowering TA that don't actually work because they don't include aeration.

acid - lowers TA and PH
aeration - raises PH and leaves TA where it is

The effect at the end is that PH is back to where it started, but the TA is lower.

Also, if you have borates in the water, things will happen much more slowly then they would if you didn't have borates in the water.
 
Jason is right. I believe I was responding to someone who wanted a chemical that JUST lowered TA without lowering pH and there isn't any (see this thread where I made my post -- the question being answered was "Shouldn't there be a jug of TA down that would make this process much faster?"). When I said that aeration is what is used to lower TA, I should have been more clear and said that it is the COMBINATION of aeration with acid addition that lowers TA. As Jason said, aeration raises pH with no change in TA while acid addition lowers both pH and TA. The net of aeration+acid is a lowering of TA.

The Lowering Total Alkalinity in the Pool School describes the procedure. As Jason pointed out, having borates already in the pool makes it more difficult to move the pH. The TA still gets lowered by the same cumulative amount of acid, however. In a 15,000 gallon pool, 38-1/2 fluid ounces (almost 5 cups) of full-strength Muriatic Acid (31.45% Hydrochloric Acid) will lower the TA by 10 ppm. If you have borates in the water, then the pH won't drop quite as much when you add the acid.

[EDIT] Larry at another pool forum put a table I wrote into a nice format that explains the procedure and also shows the effects on pH and TA of each step here. [END-EDIT]

I'm not sure why your TA went from 70 ppm to 90 ppm after you added borates and muriatic acid. The TA should only have gone up by 5.2 ppm if you added 50 ppm Borates and the pH before and after was the same.

[EDIT] By the way, if you are having that much trouble getting the pH to rise even with aeration, then you may not need to lower the TA in the first place. The only reason for the lower TA recommendation with SWG pools is that they tend to rise in pH, at least partly from carbon dioxide outgassing. If in your pool the pH is already pretty stable at the current TA level, then you can just leave it as is. Perhaps over time the pH will slowly rise and you can then add some acid to lower it and the TA will go down somewhat when you do that. In the meantime, if you want to raise the pH to 7.5 right now and can't wait for aeration to do so, you can use about 8 cups of Borax. Just keep in mind that the TA will probably rise to around 100 ppm if you use Borax instead of aerating, but this is probably not a big deal in your situation. [END-EDIT]

Richard
 

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