How often do you need to change the water in your Sous Vide machine? Given food never touches the water I don't think I need to change it every time, but it does seem like I should change it once in awhile. Any rules of thumb?

  • I would suggest changing it when you see particles floating in it, it smells off, or you catch pets drinking or playing in it.
    – SAJ14SAJ
    Apr 2, 2014 at 22:42
  • The food may never touch it directly, but how sure are you that the exterior of the bags/vessels are 100% free of any bacteria or other contaminants?
    – Aaronut
    Apr 2, 2014 at 23:38
  • 2
    @Aaronut I think the point was that the water couldn't contaminate the food, not that the food couldn't contaminate the water.
    – Cascabel
    Apr 3, 2014 at 0:06
  • 2
    I think your constraints here come from legionella danger, not from food pathogen danger. Not so sure what the max safe time for standing water is, though; the basic advice is "don't do it".
    – rumtscho
    Apr 3, 2014 at 10:03
  • Thanks All. I was just concerned that the heating of the water then cooling may make it more likely to create bacteria. Apr 3, 2014 at 13:38

1 Answer 1


The water frequently sits in the danger zone for bacterial growth, and even though it is a sealed bag, fats can migrate through the plastic (not considering contamination to the outside of the bag either from cross contamination or from juices drawn out during vacuuming/sealing).

I would suggest changing the water if:

  1. is looks dirty/cloudy
  2. it smells like anything other than water

Additionally from the PloyScience site:

Occasionally or when a cooking pouch may have leaked, simply replace the water with a vinegar/water solution and run unit at 160°F for 25 minutes to remove any residuals or lime.

So you can probably throw a little vinegar into the water to up the pH and make it more hostile to bacteria (though it will smell up the house when you use it).

  • I can attest to the fats migrating through the bag. Cooked using a brand new bath, high quality, brand new well sealed vacuum bag and a chicken breast. Water was slightly oily afterwards. Can confirm it was not the circulator or the bath as they were previously temperature tested and no oil residue was found. No contaminants were on the outside of the bag either.
    – Greybeard
    Sep 30, 2022 at 15:50

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