Septic systems are not designed to be used as a garbage disposal to process food waste or scraps. Coffee grounds and other food items will not break down in the septic tank and can even cause problems and clogging. As we’ve discussed here, a healthy septic system needs a balanced ecosystem of healthy bacteria that breaks down waste products. The bacteria helps break down human waste.
So the short answer is: NO, do not put coffee grounds down your sink drain if you live on a property with a septic system. (Actually you really shouldn’t on a city sewer system either).
Why you should not to put coffee grounds in your septic tank:
Non-decomposed solids that fail to break down will fall to the bottom of the tank and create a layer of semi-solid slug. This layer has to be pumped by a professional and hauled away. It may seem like an insignificant amount but it does add up…even if you just make one pot of coffee a day, over the course of time that ends up being pounds and pounds of grounds that will sit at the bottom of your septic tank.
The grounds will just add the the volume of solids and increase the frequency you’ll need to get your tank pumped. You’ll basically be paying to have it pumped out and hauled away- so don’t put it down the drain in the first place!
Better solutions for getting rid of coffee grounds if you have a septic tank:
Instead of throwing your used coffee grounds down the drain, there are better and more environmentally friendly ways to toss your coffee. If you do any gardening or even just have houseplants, there are several very practical uses for used coffee grounds. Compost: Over time, coffee grounds do break down in a compost pile and are great for compost.
Keep in mind that contrary to what many people think (because of it’s brown color) spent coffee is actually considered a “green” element in a compost pile. While fresh coffee is acidic, used coffee grounds are actually 2% nitrogen and with a carbon/nitrogen ratio of about 20 parts carbon to one part nitrogen they are “Green” and will need to be mixed with “brown” material (paper, cardboard, etc).
What About Coffee Filters?
Although coffee filters have the look and feel of being thin, almost similar to toilet paper, some people think that they will break down in water like tissue would. However, the appearance can be deceiving. Most coffee filters are made with 100 gram paper which is to thick and heavy to break down sufficiently in your septic tank. The filters are more likely to clog up the lint filter on your tank which will mean either taking off the riser lid from your tank and having to reach in to clean it manually or calling a maintenance service to clean the obstruction for you. In the end it will be either an unpleasant experience, expensive or both!
The best solution is to not use your septic system as a garbage disposal, food waste including coffee grounds and foot scraps should be thrown in the garbage or composted when practical (coffee grounds, veggie peels, etc). Coffee filters can also be composted. If you do not compost then the only other practical option is to throw them out. The same is true for other household paper products like paper towel, paper napkins and tissue. Speaking of paper, you can also do your septic system a favor by using a thinner, one ply toilet paper which will break down easier than standard 2 ply.
This short video is a quick example of the difference between single ply and 2 ply toilet paper and how it breaks down much quicker. We have not found the Majesta EZ toilet paper in our area, but you may be able to find it in natural food stores or larger supermarkets. There are also other RV and Camping toilet papers like this one by Camco