I just transferred my brew to the secondary fermenter (yes, it's not necessary, but I want to help clarify the brew). Where we live, we have a septic tank sewer. I was just wondering if there could be any ill effects of rinsing the yeast cake from the primary down the drain into the septic?

Perhaps it would turn the septic into beer? Perhaps it would overflow up into the pipes in the house? Perhaps it could help the spetic in breaking down its (excuse the pun) crap?

Anyone done this, and noticed any ill effects?

FWIW, I've already rinsed it down the drain, so if no answers come up, I'll update with anything that happens here.

4 Answers 4


I've been doing it for several years with no ill effects that I'm aware of.

I'd say RDWHAHB and DYYC (dump your yeast cake).

  • I've yet to get my first home brew batch, but thanks for the input, I will HAHB when I can
    – CDspace
    Commented Jan 4, 2014 at 8:01

You don't have much to worry about. Your septic tank doesn't have a lot of food for the yeast to consume, and it's getting dumped into a big tank just packed full of anaerobic bacteria that thrive in those conditions. It's incredibly unlikely that yeast could ever get established given the poor conditions.


As others have said, it probably won't cause any septic problems. Consider saving your yeast cake though! It cuts down on cost, and as long as you don't introduce any additives that could contribute off-flavors for later brews it has little downside.

I find beers tend to come out better when I re-use the cake, probably due to a much higher cell count vs using dried yeast.


I wouldn't hesitate to dump cake into the sink & septic tank, but I would hesitate to use spent yeast for another batch. It seems yeast cells elongate as they reproduce & do their thing, searching for more sugars to eat. That makes them less efficient, and the dead cells can adversely affect the flavor. One article I read (long, long ago now) suggested diluting 'spent' yeast with clear pure water & letting it settle awhile, then drawing off some and using it to make a starter.

As for turning the contents of a septic tank into beer: an amusing idea, but you'd probably have to dump several sacks of sugar down the sink, and use lager yeast if you live in a cold climate. At least you wouldn't have to worry about autolysis producing off flavors. Eh?

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.