Alkalinity won’t rise above 90

[tanksjeep]

Just had pool replastered 5 weeks ago and I realize that it’s common for the TA to be low but I’ve added about (10) 16 oz boxes of baking soda 1-2 at a time for several days and as expected, I’m struggling to keep the pH in check. It’s always around 8.2. Pool is about 12,500 gal and manually chlorinated. Still getting a small amount of ‘dust’ when brushing. Should I be concerned?

 

[ajw22]

Low TA is good, high TA is bad.

You are past the plaster curing period.

TA of 90 is ok. TA of 50-70 is better.

Post a complete list of your water chemistry.

What test kit are you using?

You using PoolMath?

What Are My Ideal Pool Levels?

Use our tool to find ideal chemical levels for any swimming pool. Check TFP recommended levels on pH, free chlorine, cyanuric acid, and more.

www.troublefreepool.com

 

[JamesW]

Are you adding acid to lower the pH?

 

[tanksjeep]

I’m using the TF-100 kit and it says the TA should be 100-120.

I am not using the pool math but I will after I do a complete analysis.

I am adding acid to lower the pH but I’m having to add it daily.

 

[mknauss]

I’m using the TF-100 kit and it says the TA should be 100-120.

TA of 50 and higher is fine.
Your fill water TA is 130 ppm. You should never need to add baking soda.

 

[JamesW]

I am adding acid to lower the pH but I’m having to add it daily.

Acid lowers the pH and TA.

 

[tanksjeep]

TA of 50 and higher is fine.
Your fill water TA is 130 ppm. You should never need to add baking soda.

Mine was 70….now at 90.

I’m seeing different suggested values ranging from 50-130 but my pool is eating acid like a kid with skittles so that is why I was shooting for >100.

 

[tanksjeep]

Acid lowers the pH and TA.

Yeah, low TA is my problem.

 

[mknauss]

If you increase the TA, the pH will rise quicker. Stop adding alkalinity.

 

[tanksjeep]

Low TA is good, high TA is bad.

You are past the plaster curing period.

TA of 90 is ok. TA of 50-70 is better.

Post a complete list of your water chemistry.

What test kit are you using?

You using PoolMath?

What Are My Ideal Pool Levels?

Use our tool to find ideal chemical levels for any swimming pool. Check TFP recommended levels on pH, free chlorine, cyanuric acid, and more.

www.troublefreepool.com

FC = 3.5
CYA = less than 20
pH = 8.2 (I’ve added acid since)
TA = 90
CH = 400

 

[tanksjeep]

If you increase the TA, the pH will rise quicker. Stop adding alkalinity.

Wait…what? I thought to raise TA I needed to add baking soda? How do I raise the TA?

 

[JamesW]

How do I raise the TA?

You don't, let it drop.

 

[Rancho Cost-a-Lotta]

Use these recommended levels...

What Are My Ideal Pool Levels?

Use our tool to find ideal chemical levels for any swimming pool. Check TFP recommended levels on pH, free chlorine, cyanuric acid, and more.

www.troublefreepool.com

 

[tanksjeep]

You don't, let it drop.

How do I stabilize the pH so it doesn’t swing? It was 8.2 and I added acid and now it’s 7.4 (good). Tomorrow it will be 8.2 (or close) again. I never had this issue before we re-plastered the pool.

 

[JamesW]

Low TA and high pH make the pH more stable.

What is the CSI?

Keep the CSI at -0.3 to 0.0.

 

[tanksjeep]

Low TA and high pH make the pH more stable.

What is the CSI?

Keep the CSI at -0.3 to 0.0.

CSI is .06 with the pH at 7.6….it shoots up to .65 when the pH rises to 8.2.

 

[ajw22]

TA - Further Reading

www.troublefreepool.com

PH TA Relationship - Further Reading

www.troublefreepool.com

 

[sande005]

You have the relationship reversed.
Higher TA pushes pH to rise. You then add acid to lower pH, and it lowers TA A LITTLE BIT. But the pH bounces back up due to the still high TA. Your TA moves slowly lower and lower, after many rounds of acid adds. There will be a point where pH holds in the high 7 range for a comparatively longer period, therefor requiring less or even little acid. Likely somewhere in the 50-70 TA range.
Working against you is the high TA of the water you use to counter evaporation and other water loss. Due to that, it is very unlikely you ever will need to add anything to move TA higher. Just add water, if really needed!

And there is the balancing act with all the other parameters to keep your CSI in the correct range. Sometimes for that, you need to have the TA higher, as it is harder to change the other factors. Then you get to stay on the "add acid" train. But play with the CSI numbers in PoolMath, as CH, temp, pH and others all influence it too. So it can be like balancing a basketball on the end of a broom.

 

[JamesW]

CSI is .06 with the pH at 7.6….it shoots up to .65 when the pH rises to 8.2.

Lower TA will lower the CSI.

 

[tanksjeep]

TA - Further Reading

www.troublefreepool.com

PH TA Relationship - Further Reading

www.troublefreepool.com

Thank you! The second link is where I determined that I needed to

You have the relationship reversed.
Higher TA pushes pH to rise. You then add acid to lower pH, and it lowers TA A LITTLE BIT. But the pH bounces back up due to the still high TA. Your TA moves slowly lower and lower, after many rounds of acid adds. There will be a point where pH holds in the high 7 range for a comparatively longer period, therefor requiring less or even little acid. Likely somewhere in the 50-70 TA range.
Working against you is the high TA of the water you use to counter evaporation and other water loss. Due to that, it is very unlikely you ever will need to add anything to move TA higher. Just add water, if really needed!

And there is the balancing act with all the other parameters to keep your CSI in the correct range. Sometimes for that, you need to have the TA higher, as it is harder to change the other factors. Then you get to stay on the "add acid" train. But play with the CSI numbers in PoolMath, as CH, temp, pH and others all influence it too. So it can be like balancing a basketball on the end of a broom.

Thank you.
I guess I was trying too hard to stabilize my pH and thought that the low TA levels were the culprit causing me too add 10-15 oz of acid a day. I just never had to do this before the replaster.