Does chlorine kill yeast?

Question

Does chlorine in tap water kill yeast? Does chloramine kill yeast? Specifically Lalvin 71B wine yeast? Is it OK to use filtered tap water (Culligan filter) to re-hydrate yeast?

Answer 1

Yes and Yes. Chlorine and Chloramine are both used to sanitize. Killing bacteria, fungi, and yeast is why they are added to water supplies. They kill the things that make you sick...and things that make you happy. There is no discrimination.

Allowing your water to sit overnight or by filtering it (with filters that say they get Chlorine out) usually will get the job done for Chlorine.

Chloramine is a bit tougher. For it you need an activated-charcoal filter or use Campden tablets (potassium metabisulfite). I typically just use a Campden tablet. They are available in your local HBS and are not very expensive.

I have only used tablets. Typically I use 1 tablet for 20 gals of water.

Recommended dose of Campden Tablets to remove chloramine

For more information on getting rid of Chlorine and Chloramine see: What are the various ways to remove chlorine/chloramine from tap water?

Answer 2

Chlorine and chloramine both kill microbes including yeast. Bleach is used as a disinfectant after all. But the key is chlorine concentration.

Bleach, for example. will kill microbes (including yeast) in two or three minutes. Tap water is chlorinated to a level where the chlorine and chloramine can take care of any remaining microbes while the tap water sits in the pipes (typically for several days before it reaches your home). The lower chlorine levels make it safe to drink, as opposed to bleach.

So chlorinated tap water won't kill your yeast. Higher levels of chlorine compounds will.

A much bigger problem with chlorinated tap tap water is that the chlorine will have a bad effect on the flavor of your beer by creating a compound known as TCP (trichlorophenol) during fermentation. This gives the beer an antiseptic, hospital-gauze like flavor.

Heavily chlorinated tap water should be carbon-filtered, treated with Campden tablets (sodium metabisulphite) or boiled and then cooled overnight to remove the chlorine compounds in order to avoid off-flavours in the beer. Your yeast, however, will not be in jeopardy if you don't do this, just the beer flavor.