Is my TA too high?

[langerking]

Back on July 6th my pool would have measured something like this:
(didn't own a real test kit, that's why I say would have measured)
FC - 3.0
CC - 0.5
pH - 6.8
TA - 20
CH - 130
CYA - 250

I was still listening to pool stores a few days earlier and they told me to add 33 lbs of Baking Soda. I added (3 lbs at a time over a period of about 4 days) and after adding 25 lbs I saw that my TA was almost 100. That is when I turned to the internet and found this forum. I joined July 12th and today (Aug 24th) I finally feel that my pool chemistry is under control:


FC = 10 (and falling, just coming out of a SLAM)
CC = 0
pH = 7.6
TA = 110
CH = 120
CYA = 38

The TA is a bit on the high side, wish I hadn't added quite so much Baking Soda.

Here is what I am thinking, please tell me if I am on the right track!

I shouldn't tinker with my TA yet, but rather wait and see what my pH will do during the next week or two. If it tends to drift up, then it may need some attention. Would I want to add acid to lower my pH all the way down to 7.2 and aerate? Or would I not need to lower the pH that much? It seems that the adjustment I need, if any, is small.

 

[Smykowski]

Here is what I am thinking, please tell me if I am on the right track!

I shouldn't tinker with my TA yet, but rather wait and see what my pH will do during the next week or two. If it tends to drift up, then it may need some attention. Would I want to add acid to lower my pH all the way down to 7.2 and aerate? Or would I not need to lower the pH that much? It seems that the adjustment I need, if any, is small.

I think you're exactly on the right track. 110 is nothing to be concerned about.

In fact, because your CH is on the low side, you probably shouldn't go much below 7.5

 

[Patrick_B]

+1 on what smykowski said. 110 and 7.6 is no concern.

 

[chem geek]

In fact, because your CH is on the low side, you probably shouldn't go much below 7.5

It's a vinyl pool ("4) Vinyl" in the signature) so the saturation index (primarily the combination of pH, TA and CH) doesn't matter if it's low. If the pH is fairly stable, leave the TA alone. If the pH rises too quickly for your taste, then you can consider lowering the TA.

 

[Smykowski]

My bad. I saw inground and assumed plaster. Disregard my statement about CH.

Thanks for the catch.

 

[langerking]

In fact, because your CH is on the low side, you probably shouldn't go much below 7.5

It's a vinyl pool ("4) Vinyl" in the signature) so the saturation index (primarily the combination of pH, TA and CH) doesn't matter if it's low. If the pH is fairly stable, leave the TA alone. If the pH rises too quickly for your taste, then you can consider lowering the TA.

Thanks for the replies everyone!

Chem geek,
If I find that I want to lower my TA somewhat, do I take the pH all the way down to 7.2 and aerate to get the TA down? Or maybe only down to 7.4, since I don't have to get the TA down very much.

 

[chem geek]

It's more efficient to lower the pH more for the lowering process since carbon dioxide outgasses faster at lower pH. See this chart to see how much extra carbon dioxide there is in the water at various pH and TA levels. So it's really up to you. It's much easier to lower the TA in spas because of the ease in generating lots of aeration from spa jets and the smaller spa volume has a larger surface area to volume ratio (outgassing rate depends on water-air surface area).

 

[langerking]

It's more efficient to lower the pH more for the lowering process since carbon dioxide outgasses faster at lower pH. See this chart to see how much extra carbon dioxide there is in the water at various pH and TA levels. So it's really up to you. It's much easier to lower the TA in spas because of the ease in generating lots of aeration from spa jets and the smaller spa volume has a larger surface area to volume ratio (outgassing rate depends on water-air surface area).

Ok, well I am not a chemistry scholar so that chart is pretty overwhelming.

Let me rephrase my question: if I were to put muriatic acid in my pool lowering the pH to 7.2 and then start aerating, there is no likelihood of getting my TA lower than I want? Say I was targeting the 80-90 range, I wouldn't end up going to a TA of 60 and now needing to add Baking Soda again?

 

[Smykowski]

You need 45oz. of 31.45% MA to lower pH to 7.2, which will drop your TA by about 8. So no....no chance of overshooting.

In your case though, I wouldn't proactively lower TA. Just keep pH in range, and TA will naturally settle where it wants to be.

As an example, I have a TA of 100, and I haven't put MA in my pool at all this year. pH is rock stable between 7.2 and 7.4

Let the pool find it's happy place.

 

[langerking]

You need 45oz. of 31.45% MA to lower pH to 7.2, which will drop your TA by about 8. So no....no chance of overshooting.

In your case though, I wouldn't proactively lower TA. Just keep pH in range, and TA will naturally settle where it wants to be.

As an example, I have a TA of 100, and I haven't put MA in my pool at all this year. pH is rock stable between 7.2 and 7.4

Let the pool find it's happy place.

Great, thanks!!

 

[pwrstrk]

+ 1 ^. My TA is 80 and my PH is also in the 7.2-7.4 range. It drifts up when the pool is getting alot of use, then it will drift back down to 7.2. It's on the low end of the range but in range. I guess that's where it likes to be. I've never had to use MA. Its not broke so I don't fix it !

I wouldn't sweat a TA of 110.

 

[langerking]

Would appreciate feedback on this again. The pool water looks and feels great, the FC is quite stable, losing only 1 or 2 ppm a day, I am only having to add 30 to 40 oz of bleach to get back to my target of 5.

But the pH and TA have drifted up a bit: pH from 7.6 to 7.7 and TA from 110 to 120. Should I act now and only have to make a small adjustment, or better to wait and see where things go? This is strange for me because back in the day when I used pucks I was drifting heavily towards acidic and couldn't keep enough pH -up and Alkalinity -up in my cabinet.

FC = 4
CC = 0
pH = 7.7
TA = 120
CH = 120
CYA = 35

 

[pwrstrk]

How fast did it raise from 7.6 to 7.7 ?

 

[Smykowski]

This is all normal, and expected after going away from pucks. Generally speaking, as long as you keep pH where it should be, TA will follow, and the pH drift will slow down. How big of a pH change you make at a time is up to you.

 

[Bama Rambler]

If the pH is steadily but slowly drifting up, I'd lower it back to about 7.2 whenever it gets to 7.8 or so until your TA gets to about 70 or 80 see what happens then.

 

[langerking]

How fast did it raise from 7.6 to 7.7 ?

about 4-5 days.

 

[pwrstrk]

Like Bama said, let it get to 7.8 and lower it. Your PH might want a lower TA. Won't hurt to try.

 

[langerking]

Thanks again, everyone!

 

[langerking]

If the pH is steadily but slowly drifting up, I'd lower it back to about 7.2 whenever it gets to 7.8 or so until your TA gets to about 70 or 80 see what happens then.

So the drift continued and my pH was very close to 8.0 yesterday morning. I hit it with 61 oz of MA and the pH registered 7.2, while the TA came down to 90. Then I started aerating and just a few minutes ago I measure and my pH has climed to 7.5 but the TA has also gone up. After 10 drops the solution was grayish, the 11th drop made it go pink so I'm gonna call it 105. This has unfolded in just over 24 hours (maybe 26-27). I am going to stop the aeration for now and see where things end up.

 

[pwrstrk]

When your doing your TA test are you wiping the tip of the bottle with a damp cloth before you start and after each drop to remove static electricity ?