Your morning coffee routine might be serving up more than just caffeine. I mean, when was the last time you actually cleaned your coffee maker? And I’m not talking about rinsing the pot—I’m talking about really cleaning it. If you spot mold anywhere on your machine, it’s time to take action immediately. But here’s the thing most people don’t realize: the mold you can’t see might be even worse.
The disgusting truth about coffee makers
According to research from the National Science Foundation, about 50 percent of coffee makers have yeast and mold growing in their reservoirs. That’s basically half of all machines out there. And it gets worse—roughly one in 10 coffee makers actually had coliform bacteria, which is found in feces. Yeah, you read that right. Every time I’ve looked into this topic, the statistics are pretty shocking. But the reality is that coffee makers create the perfect environment for all this gross stuff to grow. They’re dark, they’re moist, and honestly, most of us don’t clean them nearly enough.
The water reservoir is where most of the problems start. You can’t always see what’s growing in there, which makes it super dangerous. And that slime you might feel inside? That’s not just mineral buildup—it could be bacterial growth or mold.
Why mold loves your machine
Mold thrives in dark, damp places. Your coffee maker checks both boxes. The water sits in the reservoir, sometimes for days if you don’t use it daily. And the internal tubes and chambers? They stay moist basically all the time. After trying to clean my own machine, I realized just how many hidden spots there are where water can collect and never fully dry out. The heating element warms things up, which actually makes it even better for bacterial growth in some cases.
Signs you need to clean immediately
Visible mold is the obvious one. If you see any black, green, or white spots anywhere on your machine, that’s your sign. But there are other indicators too. Does your coffee taste off lately? Kind of musty or just not right? That could be mold affecting the flavor. Some people have reported getting sick—stomach issues, digestive problems—from dirty coffee makers. One person on Houzz described having ongoing intestinal issues that stopped completely after they deep cleaned their machine. I’ve noticed that when my coffee starts tasting weird, it’s usually time for a cleaning.
And if you see any slimy residue in the water reservoir or on the viewing window, that’s a major red flag. That slime is biofilm—basically a colony of bacteria and mold living in your machine. Not exactly what you want in your morning cup.
How often should you actually clean it
If you use your coffee maker every day, you should deep clean it every two weeks. At least that’s what the experts say. But honestly, most people probably go months without doing it. The last time I ordered a new coffee maker, I promised myself I’d keep up with cleaning—that lasted maybe a month before I got lazy again. Daily maintenance helps a lot though. Rinsing the reservoir and carafe after each use can prevent a lot of buildup. It’s pretty simple and takes less than a minute, but it makes a huge difference in preventing mold growth.
The vinegar method that works
White vinegar is your best friend here. The process is called decalcifying, and it’s basically the most effective way to clean your machine. You fill the water tank with equal parts water and white vinegar—a 1:1 ratio. Then you run a brew cycle until the carafe is about half full, and let it sit for a bit. After that, you finish the cycle and run plain water through at least twice to rinse out the vinegar taste.
For single-serve machines like Keurigs, the process is pretty much the same. Pour the vinegar mixture into the reservoir, run a cycle without a pod, wait about 30 minutes, then flush with plain water. If your machine is really disgusting—and let’s be honest, some of them are—you can increase the ratio to 2 parts vinegar and 1 part water. I mean, it won’t hurt the machine, and it’ll definitely kill more of the nasty stuff growing in there.
What you can’t reach with vinegar
Here’s the problem though. Those internal tubes that carry water from the reservoir to the brewing basket? You can’t really get in there to scrub them. The vinegar helps, but if there’s serious buildup or mold colonies established in those tubes, it might not be enough. Some people use Q-tips to clean every surface they can reach, which is smart. But those hidden passages are basically impossible to access mechanically. Why doesn’t someone design a coffee maker that comes apart for proper cleaning? Seems like an obvious solution.
When cleaning isn’t enough anymore
Sometimes a coffee maker is just too far gone. If you’ve neglected cleaning for years—not judging, but it happens—the mold might be too established to fully remove. If you clean it thoroughly and your coffee still tastes off, or if you keep getting sick even after multiple cleanings, it might be time to replace the whole machine. And if you see mold growing back within days of a deep clean, that’s telling you the contamination is pretty severe. The machine isn’t that expensive compared to your health, honestly. A new coffee maker costs what, maybe the equivalent of a couple weeks of coffee shop visits? Worth it if the old one is making you sick.
According to information from Reviewed, there are several good replacement options at different price points if you do need to start fresh. But before you toss your current one, definitely try the vinegar method at least twice.
Prevention tips that actually help
The best approach is not letting it get gross in the first place. Empty the water reservoir completely when you’re done brewing—don’t let water sit in there all day or overnight. Leave the lid open so the reservoir can dry out between uses. This reduces moisture and makes it harder for mold to establish itself. Wash the carafe and filter basket daily, which most people do anyway. But that reservoir is key. After trying different approaches, I’ve found that just dumping out the water after each use and leaving everything open makes a huge difference.
And run that vinegar cycle every two weeks if you’re a daily user, or at least monthly if you use it less often. Set a reminder on your phone or whatever. Basically, treat it like any other kitchen appliance that touches your food and drinks. You wouldn’t use a moldy plate, so why use a moldy coffee maker?
The bottom line on coffee maker mold
Look, coffee makers are gross if you don’t clean them. That’s just the reality. But it’s totally fixable with regular maintenance. Check your machine today—right now, honestly—for any visible mold. If you see it, clean immediately with vinegar. If it doesn’t come off or keeps coming back, it’s time for a new machine. Your morning coffee shouldn’t come with a side of bacteria.
