Testing Star San

I feel like I go through a lot of Star San and would like to know how I can test my mixed solution before using it to insure it works if it wasn't mixed fresh?

I mix it, then seal it in a bucket and usually use for that week or less then remix. I'd like to know if it's still good before pouring it out.

It's PH based, but not sure how to test the PH.

You need a pH meter to test pH...or pH strips if you can get some with an acceptable range.

There’s a sticky about a podcast with Charlie Talley. If I remember correctly he said if it’s pH below 3 or not cloudy, it’s good.
https://www.homebrewtalk.com/f11/charlie-talley-five-star-chemicals-notes-brewcasts-58928/

It turns cloudy if you mix it with hard water. If you use RO or distilled, I would think it would keep forever. I use RO in my spray bottle and I’ve never had to throw any of it out. I mix it every month or so.

It's definitely worth using distilled water when mixing up a new batch of Star San. Then once it goes somewhat cloudy it's time to pitch it.

But if you'd really like to know if it's good with some greater accuracy, then you'll have to invest in a cheap ($30) pH meter and test it. If it's below 3.5, then you're okay. Test strips aren't very accurate, so I'd advise against using them.

I'd advise that you invest in a better pH meter (around $80) and get a meter that can read in the hundredths (x.xx.) You could use that pH meter for testing the pH of your mashes as well as guaranteeing your Star San is still good.

I bought the cheap pH meter first and it only read into the tenths (x.x). It was only accurate to plus or minus .3, so if the meter was reading 3.5, then the pH could have been anywhere from 3.2 to 3.8. That's not accurate enough for our purposes. Money wasted but lesson learned.