What causes constant TA drops?

[nitz369]

Hey everyone been awhile since I posted.

In Feb I drained my pool, it has taken me awhile to get everything right as far as balancing goes. I finally have everything in there including borates and I can't understand why my TA is constantly dropping.

TA was down to 30 and raised to 100 about 2 weeks ago. TA is down to 60 already and I am using a ton of acid.

Current reading:
TC - 4
pH - 8.0
CH - 300
TA - 60
Borates - 50
CYA - 50

 

[crookm11]

Are you using the acid to lower your PH? If you are then everytime you add the acid you are also lowering your TA. Why are you using so much acid?

 

[duraleigh]

Why are you using acid? Is your pH constantly rising?

Baking Soda increases TA

 

[nitz369]

Yes I am going through 2 gallons of acid per week, Every other day it seems to be up to 8.0.

 

[JasonLion]

There are basically two things that raise the PH in a pool more than one year old: aeration and the occasional off brand of bleach that includes excess lye. Which leads to two questions, what do you have that causes aeration: SWG, fountain, waterfall, kids splashing, etc? And, where are you getting your bleach/liquid chlorine?

 

[nitz369]

Interesting, There is 0 aeration going on in the pool during this timeframe and the bleach is Walmart brand. So could it be Walmart brand Bleach?

 

[JasonLion]

It could be, though it seems unlikely. We have lots of people using WalMart bleach around here and you are the first to report PH rising problems.

 

[chem geek]

Is the quantity of acid you are adding per time period (say, per week) the same when the TA was high vs. when it is low? If the amount of acid drops as the TA drops, then the pH rise is at least partly from carbon dioxide outgassing so would be worse at higher TA. If the quantity of acid per week doesn't change much with TA, then the source of rising pH is some sort of base such as plaster curing (unlikely in your situation), excess lye in bleach, etc. Leave your TA at around 50-60 ppm and see the quantity of acid you need to add. Also, don't lower the pH below 7.5.

 

[JamesW]

A 2 HP pump is kind of big for your 12,000 gallon pool; is there some reason for such a large pump?

Are you using the solar? If yes, does it cause any air in the returns? If the vacuum release valve is not closed, then it will allow air into the return stream. The combination of heating and aeration would cause a lot of carbon dioxide loss.

What material is your pool, concrete, vinyl liner, fiberglass or tile?

What is your water temperature?

When you add acid how much are you adding each time?

What is your target pH when adding acid?

 

[solarboy]

Why did you drain your pool, was it for re-plastering or concrete repairs. I believe this causes pH to rise.

 

[nitz369]

A 2 HP pump is kind of big for your 12,000 gallon pool; is there some reason for such a large pump?

Are you using the solar? If yes, does it cause any air in the returns? If the vacuum release valve is not closed, then it will allow air into the return stream. The combination of heating and aeration would cause a lot of carbon dioxide loss.

What material is your pool, concrete, vinyl liner, fiberglass or tile?

What is your water temperature?

When you add acid how much are you adding each time?

What is your target pH when adding acid?

2HP is what came with it when I bought it, I have been looking into Pentair Variable Speed Pumps recently.
I am using the solar and I did think about it, when it turns on in the morning it pushes all of the extra air out of the system, system has large bubbles for 10-15 seconds. The pool is concrete. Water is up to to about 78. I haven't been super accurate when adding acid lately, I will look at the calculator and if it says 35oz I dump in what I feel o be 35oz. then restest, if I am off I add a little more, generally I have been pretty good with it, I have never added too much. I generally shoot for a 7.5pH.

Last summer I kind of neglected the pool and did half tests throughout the summer, the pool was fine but I didn't spend the time on it that I needed. I drained the pool because CH was up to 1200.

My process right now has been to test every other day, the FC usually is getting a 180oz bottle of bleach every 3-4 days, and whenever I test pH it is always high. I really want my pH to remain stable.

 

[JamesW]

Try keeping the pH higher. Try keeping it about 7.7 to 7.9. Keep an eye on your CSI to make sure that it does not get above +0.3 and you won't get scaling. You could even go to 8.0 as long as you're careful not to allow it to go higher.

Note: Not everyone will agree that allowing the pH to get to 8.0 is a good idea. I do it all of the time and do not have any problems. However, this is more my opinion than generally accepted practice.

Also, get a second opinion about the pH result. When I read the pH as 7.8, most other people read it as closer to 8.0. It can be tricky to get a good read on the pH because the color can be difficult to match.

You should also make sure that you don't have copper or iron in the water before keeping the pH higher, as a higher pH will cause metals to precipitate out more readily.

[edit]I probably should not have suggested that someone could go as high as 8.0 on their pH even if I did say it was my opinion. I will withdraw that suggestion as it could end up causing someone problems.[end edit]

 

[duraleigh]

The biggest problem I see with 8.0 pH is many tests don't read any higher than that so the pH could actually be higher.

I agree with JamesW.....that's an opinion and NOT a generally accepted practice. I also agree with the 2 or 3 other reasons he gives for NOT running your pH that high! :lol: :lol: