When taking hydrometer readings, is it acceptable to return liquid to the fermenting vessel after taking a reading in a vial? Must the vial/measuring cylinder and hydrometer have been sterilised to make this an acceptable practice?

2 Answers 2


I don't re-introduce from the hydrometer vial, the four books I've read on homebrewing (Papazian, Miller etc...) suggest that you don't because this is a place where you can contaminate your beer.

I doubt that there is a large risk because you've sanitized it all, but, I prefer to not take risks I only take a couple hydrometer readings so I don't lose that much beer.

I also take this time to enjoy the flavour of the product.

  • 2
    Agreed on tasting the sample, it's interesting to see how the taste changes as it ferments.
    – benr
    Nov 8, 2010 at 21:38
  • @benr I usually find it tastes completely awful until it's had enough time to mature! The one exception was a blackberry port which tasted amazing right from the off. Nov 9, 2010 at 10:55

I put the liquid back in, just because I don't want to lose a pint or more across all the readings. To do this I sanitize the hydrometer and the thief, inside and out, before taking the sample.

  • How many readings are you taking?
    – spoulson
    Nov 8, 2010 at 21:52
  • 1
    Not many, but the thief holds maybe 4-6 oz, so even three readings puts you down a pint.
    – benr
    Nov 8, 2010 at 21:56
  • 1
    Not if you drink the samples.
    – Denny Conn
    Sep 23, 2011 at 0:42

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