I've seen lots of discussion here about how long star san will keep, and I myself can use the same five-gallon batch for months without seeing the pH rise above 2.
However, when I mixed up a fresh batch tonight, the pH was up around 7-8. Has anybody else seen this? Is there something about how long you can keep the undiluted star san in its original bottle? I add that my original bottle was stored in a cool room, ~60-65F, and in the dark.
Any ideas are appreciated.