pH and TA all over the place

[Cetanorak]

We had a new roof put on 8/9. The pool was tarped but the tarp was full of nails and shingle material and had taken on some water, therefore the roofing materials were marinating in the water for several hours, and that water eventually made it's way back into the pool.

Ran TF-Pro tests the next day on 8/10 and pH was a magenta color that was off the charts alkaline and TA was 130.

In the evening on 8/10, I added the PoolMath recommended amount of Muriatic Acid to drop the pH to 7.2 and turned on water feature to raise pH via aeration.

The next morning on 8/11 pH was 7.5 and TA was now 40. PoolMath recommended adding about 9lbs of baking soda which I did not do immediately. Instead I added fill water (pH 7.8, TA 160). Tested again a couple hours later and pH was 8.2 (or higher?) and TA was 80.

Tested on 8/12 and now pH was 7.8 and TA was 50 so I added 3lbs of baking soda to target TA of 60.

Tested again today, 8/14, and now ph is very high again rich pink magenta color so 8.2 or higher and TA is 250!!!!

At this point, I seem to be bouncing back and forth between low and high TA. Should I be taking more subtle steps and waiting much longer between the steps? Pool pump runs several hours after any chemical addition that I make, so mixing should be thorough prior to testing.

 

[Donldson]

It is impossible that your TA would jump 200 ppm with 3 pounds of baking soda, so the first thing to ask is: are you using any other method of testing than your TF-Pro?

If you are only using the TF-Pro for testing, how old are the reagents?

 

[Cetanorak]

It is impossible that your TA would jump 200 ppm with 3 pounds of baking soda, so the first thing to ask is: are you using any other method of testing than your TF-Pro?

If you are only using the TF-Pro for testing, how old are the reagents?

I am only testing the with TF-Pro set and I purchased new reagents in September of last year. The results that I'm seeing definitely does make me feel like I must be doing something wrong.

Based on the latest test results, mentioned above, of pH 8.2 and TA of 250 it was recommended that I drop pH to 7.2 with 141oz MA. I decided to take it slow and add only 40oz of MA. I'll let that mix for a couple of hours, re-test and see where I'm at.

 

[pjt]

TA was 130

The next morning on 8/11 pH was 7.5 and TA was now 40

Tested again a couple hours later and pH was 8.2 (or higher?) and TA was 80.

TA is 250

There's no way your TA fluctuates that rapidly. There's testing error. Confirm you're using a 25 ml sample and not 10 ml. Confirm you're using the stirring device. Read the instructions carefully and follow them like a checklist.

For the TA test, keep adding (and counting) drops until there's no additional color change.

PoolMath recommended adding about 9lbs of baking soda

PoolMath is just a calculator. It's important to not blindly follow it's output.

added 3lbs of baking soda

Stop adding baking soda. Under normal circumstances, a non-trichlor pool will never need baking soda. Additionally, your fill water has high TA, so every time you top up, you're adding TA.

Take a breath and let things settle for a day. Do not add any more baking soda (probably forever). Focus on managing your pH in the 7s and let the TA settle out where it's happy. Don't chase a magical TA number, it's the least important parameter of your water chemistry. Post a complete set of chemistry readings from your TF-Pro and enable PoolMath log sharing.

 

[Cetanorak]

Stop adding baking soda. Under normal circumstances, a non-trichlor pool will never need baking soda.

Do not add any more baking soda (probably forever).

You’re correct, in the 2 years I’ve owned the pool I have never added baking soda or taken any action directly related to TA readings. I’ve only added the 3lbs of baking soda (days ago) at this point and will let everything settle, do a full battery of tests and report back/share logs.

As far as the TA test goes, I’ve been using the 25 mL flask. Mixing with the electric stirrer I add 2 drops of 7, 5 drops of 8 and then add drop by drop of 9 until solution turns and remains pink in color, multiplying that count by 10.

 

[pjt]

until solution turns and remains pink in color

Keep adding drops until there's no additional color change. For me, it's 2-3 more drops after the initial color change.