I measure out all my water in the morning and use lactic acid to adjust pH to 5.3 @ 69 degrees. I will check it after 20 minutes and it reads the same. However after 1-2 hours I check the pH and typically find it has rose to 5.5-6 pH or higher.
Is this typical? Do I need to wait longer for the pH to settle?
Another possible factor is I usually do not add the full calculated acid addition because it always lowers the pH too much when I take the initial reading or even after 15 minutes. I have thought about adjusting my water the night before with the full calculated amount to give it time to settle and take the reading in the morning?