Many things can clog the drain of your kitchen sink. Ingredients from home brewing, such as yeast and hops, can clog a drain quickly. While yeast can keep your septic system working by keeping the bacteria alive, it does not unclog drains. If yeast is clogging your drain, it's most likely mixed with grease, hair, dirt or other items. Try plunging the drain first, but if that doesn't work, you can use a combination of vinegar and baking soda in your drain.
Scoop out any excess yeast or other food in your sink with your hands. Make sure to wear rubber gloves. It will make it easier to unplug the yeast clog if other filth is removed first.
Use a plunger and plunge the drain at least 15 times. Try running water to see if the sink is still clogged with yeast.
Pour a 1/2 cup of baking soda down your drain and then add a 1/2 cup of white vinegar. Don't get too close to the drain when adding the vinegar, because there will be a chemical reaction. Also, don't run any water down the drain.
Wait for at least 15 minutes and you should see the yeast come up through the drain. Make sure to wear safety goggles when you are near the drain.
Scoop the yeast out of the sink and throw it in a garbage bag. Pour 1 gallon of boiling water down the drain and run the water to make sure the sink is fully unclogged. Repeat if necessary.