How Long Can You Leave Water in Keurig Reservoir?

Coffee Geek Lab / How Long Can You Leave Water in Keurig Reservoir?
Yurii Brown

Certified Barista

November 17, 2021

How Long Can You Leave Water in Keurig Reservoir

The Keurig coffee maker is one of the most popular and efficient coffee makers out there. One of the most notable things about it is that you don’t have to fill it up with water every time you need a cup of coffee. However, there’s an important question about keeping water in the Keurig water tank: how long can you leave water in Keurig reservoir? In this article, we will explore the answer to this question in an effort to keep everything safe.

Can you Leave Water in Keurig Reservoir?

As mentioned, the Keurig coffee maker is notable for giving you the ability to keep water inside it without having to refill it and wait for it to get reheated. Keurig works with its own coffee pods, known as K-cups. That means that it is suitable for one-time usage. You can make one cup of coffee with every pod and for the next cup, you’d have to put in a new pod. However, with many coffee makers of this type, you would have to refill the water reservoir. Keurig allows you to prevent going through so much hassle for extra cups of coffee. 

Keurig coffee makers can keep 1-2 Kg (40-80 oz) of water inside their reservoir. This amount can give you up to 10 cups of coffee. This ability was originally built into this coffee maker so if you wake up in the morning and want a quick cup of coffee in under 1 minute, you don’t have to be bothered much. That is why the recommended amount of time before you have to empty your Keurig reservoir is 12 hours and not more. A lot of people tend to leave water in coffee maker overnight, and some other people who pass this extra hassle of emptying and refilling it again for a few days. They leave the water in the tank for several days and use the same water for making coffee. There are several problems with that, which is going to be discussed next.

What Happens When You Leave Water in Coffee Maker Overnight

Leaving water in Keurig for a long time, more than 12 hours, can pose serious health threats. Keurig keeps its reservoir in a dark and damp condition. This is the perfect environment for bacteria to grow inside the reservoir. According to the NSF International Household Germ Study, 50% of the mold and yeast existing in households live inside the water reservoirs of coffee makers. [1

It is true that most of the bacteria die at 170 degrees fahrenheit, but the temperature inside the tank doesn’t always stay the same. It is a great practice to start the coffee maker and heat the water reservoir up to prevent bacteria from growing in it, that is why you can try the hottest coffee makers, as well. That alone wouldn’t help with the water that has been staying in the Keurig reservoir for several days, though. That water is contaminated and not healthy to drink. So, it is better to make sure you don’t leave water there in the first place. Keeping your coffee maker dry will prove to be much less work. You might think using the same water after several days is easier, but the measures you would have to take to clean your Keurig water reservoir is much more than that. Let’s see how you can clean your Keurig water reservoir in case it is filled with mold and bacteria.

How to Take Care of the Keurig Water Reservoir

You could easily just use a coffee maker with a removable water reservoir so that you can clean and refill it easier. However, one cannot simply ignore the quality of a Keurig coffee maker. You already know how long you can leave water in Keurig reservoir, which is no longer than 12 hours. So, if you have one, and it is contaminated due to keeping water inside it for a long time, there are several ways to take care of the water tank. 


Descaling means removing all the minerals and calcium that builds up inside the water reservoir. You may have noticed that when you boil hard water, a thick layer of minerals remains in the container after having used that container for some time. This is also the case with coffee maker water reservoirs. The Keurig water reservoir needs to be descaled every 4-6 months. One thing you can do to make sure not too much calcium and minerals get piled up inside your reservoir is to use bottled water or filtered water that doesn’t contain too many minerals. AN easy way to do descaling is using vinegar, baking soda, or Keurig Descaling Solution to clean the tank. Just fill the tank up with the solution, clean, and repeat for a few times. 


This process should be repeated every week. A water reservoir in a coffee maker is just like any other dish in the kitchen and needs to be washed. The best way to go about doing this is dismantling the coffee machine to get the water reservoir out. Next, you can easily use hot water and vinegar to clean all the molds and bacteria that exist. This ensures that no bacteria will remain in your water tank. You can also use baking soda to clean the tank. Remember that this water reservoir is not dishwasher-friendly, so avoid putting it in there. After you pour vinegar or baking powder mixed with water inside the tank, leave it there for a few minutes. Next, grab a brush and start scrubbing to make sure nothing is stuck to the walls of the tank. After that, simply wash it, and do it all again next week.

Running a Cleansing Brew

Remember we talked about how heating the tank up can get rid of most bacteria. This can help you now. You can easily start the machine with no K-cup in it, and wait for it to boil the water and clean the reservoir naturally. This doesn’t give you a cup of coffee, but a cup of hot water. You can repeat this several times to get all the water out. This is like shooting two birds with one stone: you clean the reservoir and you do it without having to dismantle the tank and take it out to clean.


Now that you know how long you can leave water in Keurig reservoir, you’re aware that leaving it for more than 12 hours requires deep cleaning of the water tank and more hassle. Even though there are other removable options for water tanks in many coffee makers, Keurig’s quality is still one of the top. So consider taking care of your Keurig coffee maker in the first place. You don’t have to worry about any mold or yeast if you thoroughly clean your machine every week. This is firstly for the sake of your health, and then, the quality and taste of coffee. 

Thank you for reading this article, and hope you have gotten the answer to your question. Feel free to share your thoughts and experience with us in the comments.


  1. NSF International Household Germ Study (2011). Retrieved from https://www.nsf.org/knowledge-library/2011-nsf-international-household-germ-study-exectutive-summary

Yurii Brown

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