I made my second batch of beer (ever) last Friday night, and in a few days' time I'd like to sample a bit of it so that I can check its gravity.

Provided that I sanitize all of my equipment (siphon, test beaker, hydrometer, etc.), is it safe to return the sampled wort back into my primary fermenter so that it can continue fermentation? Or is it not even worth the risk of infecting/contaminating the remaining 4.95 gallons thats already in there?

  • Ideally you should trust in the process and do your best to not disturb anything for 2 weeks.
    – DHough
    Commented Nov 14, 2016 at 17:22
  • If you want to do this sort of thing, another option is to ferment in a primary pail with a loose-fitting lid. You can easily open it up and put a (sanitized) hydrometer right in. The other advantage of fermenting in a pail is that they are very easy to clean.
    – Jeff Roe
    Commented Nov 15, 2016 at 4:05

3 Answers 3


Do not return samples to the batch.

Risk of infection is very high. Sacrificing this small amount of wort makes life easier and give peace of mind.

  • sample tubes are difficult to clean. Many are two part and need the base removed to clean properly, and sometimes take effort to reseal.
  • samples often need to sit awhile to get to a good temp and to degas. All the while exposed to contaminates.
  • hydrometer is delicate so typically we only rinse them
  • your sampler does need sanitized. But whether you use a baster or a thief, sanitizing the inside is very difficult. But this isn't an issue when wort only travels into it.

Personally I use large 50ml pipet, which is glass and can be sterilized by heat.

Also I use the plastic tube that hydro meters come in for testing. They use about 1/4 the wort as a two piece tube. So sample sizes are much smaller and no significant volume is missed from the batch, even with several samples.

  • Thanks @Evil Zymurgist (+1) - makes perfect sense. One thing you said that caught my attention: "samples often need to sit awhile to get to a good temp and to degass". Is this a necessary/good practice to use when testing, so as to yield most accurate SG? If so, what temperature should the sample be, and how long should it sit to degas (degass? de-gas?)? Thanks again!
    – smeeb
    Commented Nov 14, 2016 at 15:39
  • @smeeb you want your within tollerance of you hydrometer without correction usually 70°F, and you want the sample free of c02 bubbles especially if they're sticking to the hydrometer. Commented Nov 14, 2016 at 20:40
  • I never had problems with taking samples and returning them. With unsanitized, just clean equipment. Don't overrate the dangers of wild yeasts and what not. Your pitched yeast will become the strongest culture in the batch and push out any other wild yeast or whatnot.
    – Robert
    Commented Nov 16, 2016 at 23:31

I've read in a few places not to do this as it risks contamination.

I do it every time using a well-sanitized thief. I have never had an issue doing this.

  • Does it increase the risk of contamination? Sure.
  • Is it so risky as to avoid? Not to me.

Instead of using a hydrometer you could use a refractometer. It only requires a few drops. Then with software like Beer Smith you can do the conversion for fermented wort. You look through a prism and a blue line appears on some numbers.

This is what I did after I broke my third hydrometer. :-) Refractometers are 50ish dollar's versus 5 or 10 for a hydrometer.

  • Refractometers are not accurate once alcohol is present in the wort. The Beersmith conversions are very poor I've seen very large point variances 10+ when compared to hydrometer readings. Commented Nov 24, 2016 at 20:25

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