Like most RVers, I enjoy a fresh, hot cup of coffee in the morning, and I choose to make my coffee using a french press. When you clean a french press pot, you can’t simply pull out a filter and throw it in the trash. You have to find somewhere to dump out the coffee grounds. So, I wondered if could pour the coffee grounds down the sink into my gray tank.
You should never pour coffee grounds down your RV sink. It can clog the drain pipes, damage the tank sensors, build up on the bottom of your tank, or cause the tank’s dump valve to stick or leak.
Some people say that you can use coffee grounds to clean or dislodge toilet paper or solids from the black tank; kind of like a scrubbing agent. This will not work! Coffee grounds are not large enough to dislodge anything (like the ice cube trick), and will only build up on top of the debris even more.
Coffee Grounds Do Not Dissolve
Coffee grounds and other materials such as eggshells or nutshells, do not dissolve. Even if you use a tank treatment product like TST or Happy Camper, the grounds will not be dissolved by the chemicals or enzymes in these products.
Coffee grounds not only remain solid, but they also don’t float. They will sink down to the lowest part of your gray tank and sit there. Regular dumping of a full gray tank will wash away some of the grounds, but not all of them. Over time the build-up will get thicker and thicker, eventually causing a blockage.
Coffee Grounds Stick to Surfaces
Wet coffee grounds generally will stick to anything. If you’ve ever spilled wet coffee grounds on the floor you’re familiar with how difficult it is to wipe them up and there always seem to be stubborn grounds that will have to be swept up later.
Imagine how those wet grounds act when they go down the drain. They will stick to the sides of the drain pipes, and combine with the build-up of oils and sludge from food, coating the pipes. This eventually can cause odors in your sink, or cause clogs or slow-running drains.
Coffee Grounds Can Damage Tank Sensors
Coffee grounds in your tank can increase the chances of getting false readings from your tank sensors.
Tank sensors work by creating a small DC charge whenever the water level contacts the sensor. This electrical charge tells your control panel that the tank is, say, 1/3 full, depending on which sensor is activated.
Debris, like coffee grounds, can slosh around inside the tank while the RV is in motion. The coffee grounds can stick to the sensors causing that sensor to stay activated even though the water level is not touching it.
Coffee Grounds Can Damage the Gate Valve
When you dump your gray tank by opening the gate valve, some of the coffee grounds will be washed away out of the tank and into your sewer hose, when you close the valve, it seals up the opening. However, coffee grounds can build up in the gaps of the valve causing the valve to stick.
Leaks can be caused when debris builds up around the seals making it difficult for the seals to function properly or for the valve to close completely. Over time this can permanently damage the seals requiring you to replace the gate valve.
Dump Coffee Grounds In the Trash
There are plenty of solutions for getting rid of coffee grounds besides down the sink. The most obvious is to throw them in the trash. This is simple when you use coffee filters or Keurig cups.
I sometimes make my coffee in a french press, especially if I’m boondocking. It’s a little harder to clean the grounds out of that, but I use a paper towel to wipe the inside of the container clean. I usually try to dump my grounds on top of something absorbant like paper towels to avoid leaks in the trash bag.
Dump Used Coffee Grounds Outside
By far, the easiest solution is to dump used coffee grounds outside. Coffee grounds are organic and will not damage plants. In fact, they can be quite beneficial and will act as a fertilizer, and can even keep pests away from plants.
If you’re boondocking in the desert or in a forest with no designated campsites, fill up your coffee canister with enough water to wash out the grounds, then in one swoop, disperse the contents onto the ground to spread them around evenly.
If you’re in a campground, find a spot near a tree or bush and swirl the water around in your container, then quickly pour your coffee grounds at the base of the plants. Make sure you don’t dump them in an area where people will be walking.
Burn Used Coffee Grounds
Did you know that burning coffee grounds can be used as a mosquito repellent? You can do this right in your campfire or on a tabletop.
Save your coffee grounds and spread them out on a piece of heavy-duty foil and allow them to dry. Once you have your campfire going, set the foil with the small pile of the dried coffee grounds onto the hot coals and let it smoke. Adding bay leaves or mint leaves will help repel bugs even more.
You can also burn coffee grounds on a plate as you would incense. This is a little more tricky but is a good option if you don’t use a campfire, but you’ll still need some hot coals to make it work. Place your dry coffee grounds in a pile in a ceramic bowl or plate.
Place a piece of hot coal, or slow-burning wood, on top of the coffee. Allow it to burn and smoke to keep mosquitos away. Replace or relight the burning wood as needed.
Some Grounds In Your Tank Is Unavoidable
If you make your coffee with a french press, an espresso maker, or anything that doesn’t use a paper coffee filter, rinsing some coffee ground into your gray tank is inevitable. Try to get as little as possible down the sink.
Occasionally flushing your gray tank with a macerator, or with a product like the Rhino Blaster, will help rinse out coffee grounds and other debris built up inside your gray tank.
Wrap Up
There’s no reason why you shouldn’t enjoy your favorite method of brewing coffee when you’re out RVing. In fact, stovetop or campfire coffee brewing is a necessity when you don’t have electricity available for a household coffee maker. So, dispose of your coffee grounds outside or in the trash to avoid damaging your RV plumbing and waste tanks.