ph question

I have well water with a high ph. If I add ph down to it, and test it with a drop of the ph test fluid the ph will come down, but if I let the water in the shot glass sit overnight after testing it, the color changes back to a high ph color. If I mix water and bring the ph down, but dont use the water till the next day, will the ph have come back up? Is ph down a temporary fix with a limited time for use, or does the test fluid degrade after a day and give inaccurate results?

anyone have a clue?

pretty sure the ph wouldn change... why not set some out, test it, then test it again tomorrow???

like, get a big cup, add ph down n pour some in a smaller cup n test it in the small cup til you get it right. then do it again wit the same water tomorrow...