Why is pH increasing?

[CosmicMiami]

I have added NO chems yet my pH is increasing.

Yesterday my pH was 7.8 and today it is 8.0. Did the test twice. My TA yesterday was 130 and today it is the same. We did receive a healthy amount of rain yesterday.

My FC was 6 yesterday and is 6.6 today. I'm guessing I need to reduce the time of my SWG. But the other chems are baffling.

 

[domct203]

pH rise is somewhat common, especially in a SWG pool with a TA of 130.

Do you have any fountains, waterfalls or bubblers? Running them a lot (aerating the water) can also cause pH to rise.

 

[PoolGate]

Yep sounds like the rain aided in an aeration increase.

 

[CosmicMiami]

K. I didn't know pH would rise due to aeration. Trying to get my TA down but I guess it requires patience.

 

[bmoreswim]

Yes, the rain aerates and the SWG constantly aerates. It creates CO2 that outgasses as part of the chlorine gas creation process. It's the bubbles you see coming from the returns when the cell is running. My TA settles at around 60, which works well because that level keeps pH rise in check. pH trends upward for me but not fast at all.

 

[CosmicMiami]

Yes, the rain aerates and the SWG constantly aerates. It creates CO2 that outgasses as part of the chlorine gas creation process. It's the bubbles you see coming from the returns when the cell is running. My TA settles at around 60, which works well because that level keeps pH rise in check. pH trends upward for me but not fast at all.

Thanks. I guess it requires some patience to allow the TA to come down. The question then is how to raise pH without having a huge impact on TA? Assuming I finally get my TA down to an acceptable level of course.

I'm also looking at adjusting the time my SWG operates to reduce the FC a little and try to find a balance.

Thanks again.

 

[JoyfulNoise]

I doubt you will really need to adjust your pH up once your TA is lowered. Pool water is perfectly safe and swimmable with a pH anywhere from 7.2-8.0. So there’s no reason to target a specific pH value.

If you did need to raise pH without increasing TA too strongly, you can use 20 Mule Team Borax. It raises pH strongly with only minimal increase in TA.

 

[Demegrad9]

Aeration is the key to raising pH without any huge impact to TA. Look at Pool School -> Total Alkalinity - How to Lower. Basically the idea to use Muriatic acid to lower pH and Alkalinity, then aerate to bring pH back up, Repeat until Alkalinity is at the desired level.

Also as JoyfulNoise said, Borax or Soda Ash will both increase pH without huge impact to TA.

 

[CosmicMiami]

I guess my OCD kicks in here. I want my pool to be perfect! LOL

 

[bmoreswim]

Then just read pH to zero decimals and no rounding. So long as it’s 7 you are pretty much good to go!

 

[JoyfulNoise]

Also as JoyfulNoise said, Borax or Soda Ash will both increase pH without huge impact to TA.

No, I specifically did not mention soda ash because soda ash (aka, washing soda or sodium carbonate) will greatly raise pH AND TA. You want to avoid using soda ash for minor pH adjustments because it adds to TA which will cause a long term increase in pH above and beyond it’s immediate effect on pH.

To the OP,

There is no “perfect” in pool water chemistry. You simply try to maintain appropriate ranges and the pool water will be fine. Any source (pool store, internet, etc) that says, “X is the perfect value for pool water parameter Y” is simply wrong and does not know the first thing about chemistry.

 

[CosmicMiami]

No, I specifically did not mention soda ash because soda ash (aka, washing soda or sodium carbonate) will greatly raise pH AND TA. You want to avoid using soda ash for minor pH adjustments because it adds to TA which will cause a long term increase in pH above and beyond it’s immediate effect on pH.

Cool. I'll use 20 Mule in the future. I have soda ash now.

Love this forum.

I wonder though. What will a high TA do if anything?

 

[mknauss]

What will a high TA do if anything?

A high TA will put pressure on your pH to rise and drive CSI higher resulting in a greater chance of calcium scale. As you have a SWCG, a high TA will more readily cause scaling in the generation cell. The high pH of the chlorine generation process coupled with a high TA can cause scaling on the plates in the cell.

 

[JoyfulNoise]

High TA will result in a constant upwards pressure on pH. The amount of dissolved CO2 in pool water is directly proportional to the TA. When CO2 outgasses from pool water, pH rises. So if you have lots of dissolved CO2 in your water, your pH will rise faster.

 

[domct203]

..... As you have a SWCG, a high TA will more readily cause scaling in the generation cell. The high pH of the chlorine generation process coupled with a high TA can cause scaling on the plates in the cell.

I never realized that just a high TA would cause a scale issue in the cell. I always thought that as long as your CSI is properly managed to be slightly negative that scale would not be an issue.

 

[mknauss]

At least in my cell with our water, if my TA is above 80, my SWCG will shed scale at each polarity change. I call it my 'canary in a coal mine'. So I lower my TA and it stops. I attribute it to the high pH in the cell forcing the CSI very positive inside the cell when generating. By lowering the TA it reduces the scaling effect in the cell.

Take care.

 

[domct203]

At least in my cell with our water, if my TA is above 80, my SWCG will shed scale at each polarity change. I call it my 'canary in a coal mine'. So I lower my TA and it stops. I attribute it to the high pH in the cell forcing the CSI very positive inside the cell when generating. By lowering the TA it reduces the scaling effect in the cell.

Take care.

That’s very interesting. I surmise you have an elevated CH to begin with.

 

[mknauss]

Yes - never below 300 rising to 1000 prior to drain.