Ph Fluctuations Normal?

[DC912]

My pool was relpastered about 45 days ago. I have been using a new Taylor K-2006. Over the past 10 days, the TA has been 80, CYA is 35, FC ranges from 2 to 4, but the pH seems to fluctuate widely daily between 7.0 and 7.6. I have not tried to adjust pH, because when it changes so rapidly I am unsure which direction to adjust, or if I should adjust at all?

[waterbear]

new plaster will cause pH to rise. How are you chlorinating (I am going to assume trichlor tablets because of the pH drop to 7.0 and you did not indicate that you are adding acid.
Are you tablets in a floater or feeder? If they are in a floater are you collecting your water sample near the floater?) I assume you are not adding any other source of acid.

[DC912]

I am using liquid chlorine/bleach. I have not added anything for the purpose of adjusting pH. On the 26th in the afternoon the pH was 7.4. The following afternoon it was 7.0. The next morning it was 7.6. This evening it was 7.8. Thanks.

[Watermom]

How high is your chlorine level whenever you have been testing your pH?

[DC912]

It's ranged from 2 to 4, but I did not write down the specifics on the FC with the pH levels. I'll keep better records over the next few days.

[waterbear]

If you are doing a TA test and not rinsing the vial well afterwards and there is some liquid left inside when you do the next pH test it can cause it to read low since the TA test uses sulfuric acid as the tittrant and if any is left in the vial it can cause the pH to read low. Since you did not give us any calcium hardness readings I assume that is not being testing each time.