This might be the best place to pose this question. Does Star San have an expiration date? I have been using the same bottle of Star San and for several years, and it seems to be just fine! But, I got to wondering this week as I was Brewing if I should be looking for a new bottle. Anyone have any thoughts or experience with Star San going bad?
Five Stars puts an expiration date on the bottles and jugs, which in my mind is totally bogus. A few months back I finally finished a 32oz jug of Starsan that I had bought about 7 years ago. Still worked like it did the first day. If anything, the concentrate may have gotten a tint or 2 darker over that time, compared to the new gallon I bought.
I keep the working solution in buckets, there's always something soaking in it, and when it gets grayish or a bit too scummy to my (already low) standards, I dump it and make fresh. That's always a nice and happy day.
Now I did notice when the working solution sits for a week or longer a white chalky precipitate forms on the bottom. Racking hoses laying there also get coated on the inside with that. I pour or rack the Starsan from the top into another bucket and leave the precipitate, dust, and other debris behind. I simply run a draw brush through the hoses, rinse them out and they go back into the Starsan.
After a few (2-6) weeks, the Starsan tends to get a slick feel to it . It still seems to work fine though, but hoses and stuff feel weird. That slickness eventually disappears, and the solution becomes clearer with time. Perhaps the dodecylbenzenesulfonic acid decomposes slowly, which could change its sanitation properties. I always keep the pH under 3.0 by adding a few drops of phosphoric acid (Duda Diesel). Anything stored in that solution gets brushed, rinsed and immersed into fresh solution before use.
Some say when you use distilled or RO water the working solution won't get cloudy (as quickly). Maybe that precipitate doesn't form then either. I've never tested that.
Since I got a gallon of concentrate, I've become a bit more liberal in making fresh solutions.