pH is always rising


Well-known member
May 18, 2007
Enid, Oklahoma
Since I'm no chemist I am trying to understand why my pH is always rising to unacceptable levels. When I opened my pool this spring my TA was 290 and CH was 530. My fill water is from a well and has about the same numbers. Over the past 4 weeks I have added 3 gallons of acid (not all at once) and pointed all 5 of my returns to the surface. My TA has lowered to 180 in this time but my pH can rise to "off the scale" red in as little as three days without adding water by well or rain. I don't have a SWG and have been using 6% bleach for sanitation.

So my questions are this:

Could my return jets be causing enough aeration to have this effect on pH or could there be some other factor at work here?

Would adding Borax help keep the pH more stable?

Should I budget more money for Muriatic Acid every year?

If my pool is out gassing CO2 will it finally reach some type of equilibrium about the time I close the pool in the fall? :)

Does the high CH from my fill water cause higher CO2 concentrations which lead to out gassing and high pH?


Well-known member
Mar 29, 2007
I'm no chemist but I'll take a stab at it. Though I'm not on well water and my fill water isn't as extreme as yours (CH=300 & Alk=180) I had a similar problem with my "new" pool (just moved) after I got the pH what I thought was stable. The previous owner loaded up the feeder and when I tested the water after moving in, FC was 30 ppm and pH was >6.8 :shock: ! I immediately added Borax (ended up adding 4 boxes total) to get the pH up. Anyway, after getting that straightened out, I noticed my pH was constantly on the rise. Within one week it would go from 7.2 to 8.2 so I began aeration to lower my Alk to 100. Now it seems to have stabilized however it's only been a week so I'll give it some more time and lower Alk more if needed. Hopefully Chemgeek or Waterbear will chime in but I believe two things are happening here:
1. Your Alk is still to high causing the pH to rise. I'm not 100% sure but I believe you could run a very low (>80 ppm) with such a high CH number.
2. Yes, the jets pointed up will cause some rise in pH due to the off gassing of Co2 however I don't think this would cause it to rise as quickly as your high Alk.

I'd start to aerate and lower the Alk to around 90 ppm. I used some short pieces of hose, one end forced into the returns and the other end with an empty water bottle wire tied to it to create mini water falls at each return. My last fiberglass pool had a waterfall and two spa jets so aeration was a cinch. I came up with this "Red Neck" contraption as my wife called it to expedite the aeration process and it worked like a charm. Borax will help to stabilize Ph however it is not as simple as just adding a box or two. It is a long process of adding, lowering pH, adding some more, lowering pH and so on. I'd still get the Alk in check before attemting anything else.


chem geek

LifeTime Supporter
TFP Expert
Mar 28, 2007
San Rafael, CA USA
See this thread among others for more info on how to lower your alkalinity. A lower TA will help as will the Borates that were suggested. With your high CH, you could definitely go with a rather low TA even below 80 (but above 50).