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I keep StarSan in a spray bottle for easier sanitizing during brew day.

How long does the StarSan last in that bottle? Is it good forever?

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up vote 7 down vote accepted

Just after post the question I found the Tech Sheet on Five Star's website. It says that the sanitizer is good so long as the pH remains below 3. Since I'm keeping it in a spary bottle with distilled water it shouldn't ever get above 3.

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I've heard people say they reuse it until it starts to turn cloudy, but I'm more apt to use the pH rule, since it lasts longer.

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Do you actually test the pH? – sgwill Nov 11 '10 at 14:07
Honestly, no. I just dump it every couple times I brew. Except one time I found a dead bird floating in the star san bucket, so I obviously dumped that on. – PMV Nov 11 '10 at 14:24
pH test strips are both cheap and readily available, and plenty accurate for this use. That said, I'm not sure that I'm anal-retentive enough to test it every time, either. – Herb Nov 11 '10 at 15:24
The pH rule is the best guide - my starsan turns cloudy immediately, but it's still effective. I keep in an airtight container and test every couple of weeks, and again if it gets a bit soiled. – mdma Jan 19 '12 at 15:37

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