TA & pH/Need Clarification on the Correlation Between the Two.

Mendy48

Bronze Supporter
Apr 27, 2018
737
Midland, MI
🤦🏽‍♀️ I completely forgot that a pH reading of an FC above 10 is completely inaccurate. I was reading a recent post where someone was reminded about this. And it wasn’t until I read that post that I realized that I needed to wait for my FC to fall at 10 or below to get an accurate pH reading. Ugh.

Anyhow, my question is this. What makes a pH reading fluctuate? My TA fall from 110 to 90 (if you look at my reading log) and now that my TA is at 90, my pH is reading jumped to 7.8.

I mean, all summer I had to add borax to pull up my pH and it wasn’t until today that I had to use acid (for the first time this season) to bring my pH down.

I guess I’m just not understanding the correlation between pH and TA... and why my pH won’t stay “put”.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
22,426
Laughlin, NV

TA buffers the pH. Normally, if you are not adding high or low TA fill water, the pH and TA will find an equilibrium. Most water wants to sit at a pH of 7.8. TA can be anywhere from 50-90 ppm and be in equilibrium.

Odd that you said you had to add borax all summer, unless your pool is filled with low TA water (such as rain water). Why your pH has risen now may be you are not getting that rain as you did during the summer.
 

Mendy48

Bronze Supporter
Apr 27, 2018
737
Midland, MI
I'm getting a lot of rain right now... for days at a time.... than I did in the summer. And I decided to wait until my FC fell below 10 to check my pH, which (for the first time) was at 7.8. I noticed in my reading/testing log that I often checked my pH level when my FC was a tad bit above 10, so I may have been getting inaccurate readings for a long time. However, it didn't dawn on me that I was reading my pH at a higher FC until it was brought to my attention with an earlier post I read. So last night, I decided to wait until my FC fell below 10 to take my pH reading and that's when I realized that my pH was at a 7.8. Thus, I may have been adding borax when I really didn't need to. Not sure....

I just wanted to see why my pH would fluctuate, then again.... it could be that I was not testing it right to begin with. Not sure. But I'm getting A LOT of rain right now though. Could that explain things?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
22,426
Laughlin, NV
Normally, a FC above 10 ppm will push the pH reading higher than actual. So your data is opposite --

pH of 7.8 is fine. Your parameters indicate you have no chance of scale so I would not worry about the pH until it goes above 8 or below 7.2.
 

Mendy48

Bronze Supporter
Apr 27, 2018
737
Midland, MI
Thanks Marty!!!

Yeah! I'm not sure what was going on with my pH. I would pull my hair out trying to figure my pH out, so I'm just going to leave it alone. I already added 10oz of Acid to my pool.. very little... just to bring it down a tad bit. I'll, in the future, make sure it doesn't go above 8 or below 7,2. :) Thanks again.