Does PH ever normalize?

[chem geek]

steveinaz,

Since your signature line says you have a saltwater chlorinator, I suspect that the rise in pH you are seeing is due to the outgassing of carbon dioxide. Can you post some of your pool water chemistry numbers? In particular, if your TA is higher than 80 (assuming a CYA of 70-80 as recommended by most SWG manufacturers; if your CYA is lower, say 30, then the TA can be 70), then your pH will have a stronger tendency to rise. Also, do you have aeration features such as a waterfall?

It is true that the rise in pH will slow down at higher pH so you can just settle on a higher pH, but lowering your TA will probably be the most effective way at slowing the pH rise down and significantly dropping the amount of acid you have to add. This thread talks more about this (but it's a long thread).

Another option, done in combination with lowering the TA, is to use 50 ppm Borates in your pool (from Borax and acid addition). This thread talks more about this, but is also a long thread.

I also noticed that in this thread that you note that your pool is new and is plaster/gunite. In that case, new plaster will "cure" and release calcium hydroxide causing your calcium hardness level to increase and the pH to dramatically increase. You will have to add lots of acid to compensate for this. The above suggestions for lowering the rate of increase of pH and acid usage are still valid (as they reduce the amount of carbon dioxide outgassing which is one source of rising pH), but even doing the above you will still have a significant demand for acid until your plaster cures. This is greatest in the first month, continues high for a few months, is much lower (sometimes not noticeable) after 6 months, and may not be noticeable anymore after 1 year (though some people report noticeable acid demand for up to 2 years). If after lowering the TA and settling for a higher pH (say, 7.7) you still find you need to add lots of acid, then the curing of plaster is most likely what is going on. There isn't anything you can do about that except realize it will eventually slow down.

Richard