How long is star san good for?

Made a big batch of star San last night when I was brewing and I kept some in an empty gallon jug because I need to take gravity readings of a different brew I am fermenting. How long will it last before I need to make up another batch?

If the water is distilled and you keep it covered it'll last a very very long time, use RO and it'll last a very long time. If you used tap water, when it turns cloudy, it's time to change it. Ultimately checking the Ph is the only sure fire way to know when it's done. When it's over 3, it's done.

Edit: All tap water is different, so that's why I can't tell you how long yours will last with tap water. My tap water is very high in PH to start with, and the starsan turns cloudy almost instantly so it doesn't last long at all.

Awesome thank you. Hopefully it will not be cloudy when I need to take another reading tomorrow. Thanks.

What is RO?

mikecshultz said:

Awesome thank you. Hopefully it will not be cloudy when I need to take another reading tomorrow. Thanks.

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Glad to help. It won't go bad that fast though. No matter what water you use I'd say it's likely to be safe for at least a week. With my crappy tap water it still lasts at least two weeks, but I buy RO water and try to keep crap out of it (like rinsing things in the starsan that are not thoroughly cleaned first, and keeping a lid on the bucket) and it lasts over a month.

Edit: btw, the cloudiness is just the eye test. Cloudy starsan can be just fine to use so long as the PH is below 3. You can buy test strips if you want to conserve your starsan.

mikecshultz said:

What is RO?

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Reverse Osmosis.

I make up five gallons at a time with DI water. I will put two one gallons filled up, top off my spray bottle, and the rest is left in the five gallon bucket for quick sanitizing. Even the heavily used five gallon container lasts a month before any signs of clouding.

DI= deionized. Get it from my lab.

Just to re-emphasize, cloudy Star San does not mean it's lost its effectiveness, which is pH driven. It can be cloudy and still have an effective pH for sanitizing (i.e., below 3). With my tap water, the stuff will go cloudy almost immediately, but will remain below pH 3 for at least a month in a sealed bucket - probably longer, but I usually use it all within that time.