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How Long Can You Leave Water in Keurig Machines?

a big Keurig K-cup pod coffee maker

The best part about owning a Keurig is waking up, pushing a button, and having a fresh cup of delicious coffee ready to drink in mere minutes. A key cog in the Keurig coffee process is the water reservoir. Keeping your Keurig’s reservoir full of water cuts out the annoying step of filling the machine before brewing your coffee, but there are a few things to keep in mind to ensure your coffee is safe to drink and tastes its best.

In this guide, we’ll cover the best practices for managing your Keurig’s reservoir, including how often you need to clean it and how long you can leave water in the reservoir. If you’ve never given your Keurig’s water reservoir much thought, this is a must-read article for you.

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What’s the Problem? Bacteria

Stagnant water is a prime breeding ground for bacteria, especially if it’s warm water. Leaving your Keurig’s reservoir full of water for a few days without turning it on invites bacteria formation, which can make you sick.

The safest way to avoid bacteria buildup in your Keurig is to make sure you’re refilling it with fresh, filtered water at least every other day.

Keurig Mini side view

If you make a lot of coffee, you might already be doing this since you’re probably refilling frequently to keep up with your high coffee demand. If you only drink one or two cups a day and have an average or large reservoir, you should empty it and refill it frequently.

The situation is complicated a bit by temperature. Most bacteria thrive in warm, damp environments, but when the temperature rises too much, they start to die. Above around 170ºF, most bacteria can’t survive, making it fairly safe to drink even stagnant water at this temperature. However, most people don’t leave their Keurigs on and heating for days at a time, so it’s probably best to avoid letting the water sit anyway.

What to Do if Your Water Sits for a Few Days

Even if you’re careful to empty and refill your Keurig often, sometimes you’ll accidentally leave water in the reservoir for days at a time. You might come back from a relaxing, week-long vacation to find that you forgot to empty the Keurig before you left. What should you do?

The simplest first step is to run a few brew cycles without inserting a pod. Letting boiling water run through the machine will kill most bacteria and make your Keurig safe to use again. If you want to be extra safe, you can take the opportunity to perform a deeper clean and descale your Keurig.

drain Keurig water

Keurig makes a descaling solution, or you can make one with vinegar. Descaling is something all automatic coffee machines need a few times a year, Keurigs included. Water contains minerals that leave white deposits behind when the water evaporates. Over time, your coffee machine can build up a layer of scale that will change your coffee’s taste at best and clog your machine at worst.

Descaling your Keurig is good for your machine’s longevity, and the vinegar will help kill and clean any nasty squatters that made your coffee machine home while you were away. You should always try to remember to empty your Keurig’s reservoir when you know you won’t be using it for a few days.

Regular Cleaning

While we’re on the topic of keeping your Keurig healthy, we should mention that regularly cleaning the reservoir is probably a good idea. Some people find that their Keurig’s reservoir develops a thin layer of slimy film when they keep water in it regularly. If you discover such a layer of film on your reservoir, you should clean the reservoir and run several brew cycles with just hot water before you make coffee again. Descaling your machine is also probably a good idea in these cases since the descaling solution or vinegar will help kill anything the hot water didn’t finish off.

how to clean Keurig Mini

Our routine has evolved over the years to include regularly cleaning and scrubbing the reservoir. It doesn’t take long and is the only way to guarantee your coffee is safe to drink. As an added bonus, keeping your machine squeaky clean will also make your coffee taste better, so it’s an overall win.

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Conclusion

If you can avoid it, don’t let your Keurig sit with water in it for more than a day or two. Bacteria and mold can grow in warm damp environments and make you sick or worse…make your coffee taste weird. In all seriousness, cleaning your Keurig is a required part of owning a coffee machine; it’s essential for your health, the machine’s health, and for making the best tasting coffee possible.

Occasionally, you’ll accidentally leave the reservoir full for more than a few days, and in those cases, we recommend performing a full deep cleaning. It can be a pain, but your health is worth it. In reality, it doesn’t take long, even if you opt for doing a simultaneous descaling.

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Sean Brennan

Sean’s obsession with coffee started when he received his first French press as a gift almost ten years ago. Since then, his love of coffee – and the number of coffee gadgets he owns – has grown considerably. A scientist by training, there is no stone he has left unturned in the never-ending quest for the perfect cup of coffee. He has spent many hours tuning his pour-over technique, thinking about how to best compare grind quality, and worrying about whether the Nicaraguan or Kenyan beans will make the best cold brew. These days he favors the Hario V60, and starts each day by hand grinding his coffee before enjoying a cup prepared with care and attention to detail.

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