I hate to break it to you, but your coffee maker is probably pretty icky if you haven’t cleaned it lately. From the outside, it looks nice and shiny sitting on your counter—but if you were to look inside, there’s a good chance you’d never want to sip your coffee ever again.

According to microbiologist Jason Tetro, author of The Germ Code, if you don’t deep-clean your coffee machine, it’s going to be loaded with germs. There’s no doubt about it. “If they aren’t cleaned regularly, they quickly become gross,” he says. One survey found coffee reservoirs are one of the germiest places in a home, with 50 percent containing yeast and mold. Unfortunately, simply rinsing your machine with hot water isn’t going to cut it when it comes to cleaning.

If you really want to ensure you’re cleaning the inside of the machine where mold and build-up forms, your best bet is learning how to descale a coffee maker, which removes the mineral build-up and coffee oil residue. It not only makes your coffee taste better, but also keeps your coffee maker top-notch for longer. The good news is there are products that can help you get the job done. One of the most highly-rated options on the market is the Urnex Coffee Machine Cleaning Powder ($8), which is dissolved in water then brewed like normal, allowing it to work its magic all throughout the inside of the coffee maker.

You can also use something that’s already in your pantry. Tetro says you can descale a coffee maker by running a brew cycle with one part water to one part vinegar. As long as you’re deep-cleaning with vinegar or a store-bought descaling solution at least once a month, you’ll be able to keep the germs, mineral deposits, and mold away.

To make sure every pot of coffee tastes great, follow the easy cleaning descaling instructions below.

How to descale your coffee maker like a pro

If you’re using a descaling powder:

1. 1.
   Always follow the specific instructions on your product, as they may differ. Generally-speaking, first dissolve the cleaning powder into a liter of lukewarm water.
2. 2.
   Pour the water into your coffee maker’s water reservoir and brew the full tank without coffee grounds.
3. 3.
   After dumping out the brewed cleaning solution, refill the water tank with fresh water and brew the entire tank again.
4. 4.
   To ensure all the cleaning solution is gone, repeat the third step two more times.

If you’re using vinegar:

1. 1.
   Fill your coffee maker’s water reservoir with one part water to one part vinegar.
2. 2.
   Brew the full tank of water without coffee grounds, allowing the vinegar to deep-clean your coffee maker.
3. 3.
   Once it’s finished, dump out the water and repeat the second step one more time.
4. 4.
   If there’s a vinegar odor or taste, repeat the rinse once more with a scoop of coffee grounds.

Here’s what a registered dietitian wants you to know about coffee: