Does Ph naturally rise in the pool?

[Bosch232]

Spring is finally here and as a still-inexperienced new owner, I broke out my shiny new Taylor kit today.

Last year I only used test strips on the pool water (new guy, remember). They always said my Ph was high. I just tested with the Taylor and it's saying 8.0. Pretty high. (I have done nothing yet this spring to open the pool yet. I'm just playing with the Taylor kit.)

Now here's my question: I also rinsed and tested the water at the hose end. It says 7.0. So does ph naturally go up over time? Is this pattern telling me something? Any thoughts are appreciated.

[chem geek]

Pool water is intentionally over-carbonated to provide a pH buffer and to saturate the water with calcium carbonate to protect plaster pool surfaces. Such over-carbonation results in carbon dioxide outgassing and this causes the pH to rise over time. The rate of rise is related to the amount of over-carbonation which you can see from this chart that as the pH rises there is less over-carbonation so it slows down as the pH approaches around 8.4, depending on the TA level. You can see that a higher TA and lower pH is more over-carbonated so will outgas faster. The chart doesn't show the effect that the rate of outgassing varies as the square of the TA level, so a higher TA level can have the pH rise noticeably fast, especially if there is aeration of the water (waterfalls, spillovers, fountains, etc.).