Are Coffee Grounds Safe for Septic System Tanks?

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Septic systems are not designed to be used as garbage disposal to process food waste or scraps. Coffee grounds, food scraps and other items that will not break down in the septic tank will add to the sediment layer at the bottom of the septic tank. This sludge layer is why septic tanks occasionally need to be pumped out which can be costly. If left unpumped a septic tank can overfill, causing a foul smell and eventually dirty wastewater to overflow onto your yard or leaching field.

So the short answer is: NO, do NOT put coffee grounds down your drain if you live on a property with a septic system. The coffee will not dissolve in the tank. Adding solids, including ground coffee, to your septic system will just lead to having your tank pumped more often which will cost you money. A better solution is to compost coffee grounds, use them in your garden, or if no other option is available – throw them away along with the paper filter (if you use one).

As we’ve discussed here, a healthy septic system needs a balanced ecosystem of healthy bacteria that break down waste products. The bacteria feed off of human waste.

coffee filters and septic system
If you have a septic tank, coffee grounds & filters should go in the trash – or the compost pile.

Ground coffee beans on the other hand, while they do break down eventually if composted in the ground, will not dissolve in your septic tank and even if you are using a septic tank activator those enzymes will not dissolve coffee grounds. 

(Actually plumping experts explain that you really shouldn’t put them down the drain on a city sewer system either).

Why You Should Not Put Coffee Grounds in Your Septic Tank:

Adds to Sludge Layer: Non-decomposed solids that fail to break down will sink to the bottom of the tank and create a layer of semi-solid sludge. 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 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!

Lowers PH: The bacteria that break down the solids in your septic thrive in a neutral PH range (around 6.5-7.5). Coffee is relatively acidic (around 4.85 to 5.10). While the used grounds are less acidic after water has passed through them, they still raise the acidity of the tank especially if you are making a pot of coffee every day and dumping all those grounds down the sink. Raising the acidity will make it harder for the good bacteria and potentially lower the efficiency of the tank – leading the solids to build up and require premature pumping.

Getting Rid of Coffee Grounds with 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 its 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). 

One simple way to compost while keeping your kitchen odor-free is to get a simple stainless steel composting pail that either sits under your sink or on your kitchen counter. It takes the hassle out of composting and is a good solution for keeping coffee grounds out of your septic system.

What About Paper Coffee Filters?

paper coffee filters
Paper coffee filters don’t do well in a septic tank. Image Credit

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 the water as tissue would. However, appearance can be deceiving.

Most coffee filters are made with 100-gram paper which is too 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 food scraps should be thrown in the garbage or composted when practical (coffee grounds, veggie peels, etc). Actually, for years we were told not to even use a garbage disposal on a septic system, but things have changed-click here to see your options.

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.

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