pH NOT rising

Randrx2 · Jul 15, 2023

In the past, I have had a new build gunite pool with plaster finish and SWG. As expected, my pH was always on the rise and I controlled with muriatic acid.

Now my pool is vinyl with a SWG. I have jugs of MA anticipating the pH rise, but it just is not rising. It just stays at 7.8 all the time (although today it was 7.6, either due to rain or the fact I did the test in natural light. Usually I test inside early morning prior to sunrise). I have a sheer descent waterfall also, but I do not run it very often, maybe a couple times a week.

So what gives? I was expecting the SWG to increase the pH as it is supposed to do.

Is my TA right in a perfect balance not to cause a rise? My other thought is that my FC may be high possibly bleaching out the pH test.

I'm not unhappy with the results, just baffled.

Thanks.

FC = 9
ph = 7.6
TA = 60
CH = 110
CYA = 60
SALT = 3600
TEMP = 86.4
CSI = -.081

JamesW · Jul 15, 2023

Randrx2 said:
I was expecting the SWG to increase the pH as it is supposed to do.

It is a myth that SWGs cause pH rise.

Anode 4Cl^- -> 2Cl₂.

Cathode 4H₂O -> 2H₂ + 4OH^-.

2Cl₂ +2H₂O -> 3H⁺ + HOCl + OCl^-.

HOCl + OCl^- + uv light -> O₂ + H⁺ + 2Cl^-.

Following the process, we can see that there are 4H⁺ and 4OH^- created, which nets out to pH neutral.

The chlorine gas generated is very acidic and creates 3 hydrogen ions for every 4 hydroxide ions created.

As the hypochlorous acid is broken down by UV, 1 more hydrogen ion is created for a net neutral result.

Assuming that chlorine gain and loss are equal, there's no pH rise.

Rancho Cost-a-Lotta · Jul 15, 2023

Your fill water has a significant impact on TA and pH.

duraleigh · Jul 15, 2023

Be Thankful!. If you really dig down too far for the answer it may start to rise.

Saturn94 · Jul 15, 2023

Randrx2 said:
In the past, I have had a new build gunite pool with plaster finish and SWG. As expected, my pH was always on the rise and I controlled with muriatic acid.

Now my pool is vinyl with a SWG. I have jugs of MA anticipating the pH rise, but it just is not rising. It just stays at 7.8 all the time (although today it was 7.6, either due to rain or the fact I did the test in natural light. Usually I test inside early morning prior to sunrise). I have a sheer descent waterfall also, but I do not run it very often, maybe a couple times a week.

So what gives? I was expecting the SWG to increase the pH as it is supposed to do.

Is my TA right in a perfect balance not to cause a rise? My other thought is that my FC may be high possibly bleaching out the pH test.

I'm not unhappy with the results, just baffled.

Thanks.

FC = 9
ph = 7.6
TA = 60
CH = 110
CYA = 60
SALT = 3600
TEMP = 86.4
CSI = -.081

Since adjusting TA according to TFP recommendations many years ago, I haven’t had to add a single drop of acid. PH stays stable all season (about 7.5).

pH NOT rising

Randrx2

JamesW

Rancho Cost-a-Lotta

duraleigh

Saturn94