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How Long Can You Leave Water In A Keurig?

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Water shouldn't sit in a Keurig reservoir for more than 2-3 days to avoid bacteria or mold growth. If not in regular use, empty and dry the reservoir, preferably daily. Extended periods of non-use call for reservoir emptying and machine cleaning for optimal function and taste.

I’m Tim, the founder of Tim’s Coffee. I own a Keurig coffee machine and have learned from experience how often they should be cleaned. 

In this article, I will talk about the following: 

Keep reading to learn more. 

Key Takeaways

  • Don’t leave water in your Keurig for more than 2-3 days to prevent bacterial and mold growth.
  • Empty and clean the water reservoir at least once a week.
  • Leaving water in your coffee maker overnight is okay, even if it’s not recommended.
  • The more you use your machine, the less often you need to empty it, as the heat kills bacteria and mold. 
  • Ensure regular descaling and cleaning of your Keurig machine for optimal function and taste.

How Long Can You Leave Water In Your Keurig Coffee Machine?

Ideally, you should leave water sitting in your Keurig’s reservoir for a maximum of 2-3 days. 

Leaving water in the reservoir for extended periods can lead to bacteria or mold growth, especially if the machine is not used regularly. 

Therefore, it’s recommended to empty and clean the water reservoir at least once a week or even daily if possible.

If your Keurig will be unused for several days or more, it is best to empty the reservoir and leave it open to dry. 

This not only helps maintain the longevity of your Keurig but also ensures the best taste for your brewed beverages. 

It’s crucial to remember that regular cleaning and descaling of your Keurig machine are necessary to ensure it functions optimally and provides you with fresh, great-tasting coffee.

Should You Leave Water in Coffee Maker Overnight?

Leaving water in a coffee maker overnight might not cause immediate harm. That said, it isn’t generally recommended due to the potential for bacterial growth and the formation of mold, especially if this becomes a habit. 

However, as previously said, 2-3 days is really where this becomes a problem. So leaving it overnight, will not be a problem. 

Even though it’s okay, it’s still not recommended. 

Here’s why:

  • Bacterial and Mold Growth: Stagnant water, particularly in a warm and moist environment like a coffee maker, can create a suitable environment for bacteria and mold to grow. If you continuously leave water in the coffee maker, there’s a greater chance that such organisms could contaminate your coffee over time.
  • Taste Impairment: Water left in the coffee maker may take on stale or unpleasant tastes, which could affect the flavor of your next brew.
  • Mineral Buildup: If you’re using hard water, leaving it to sit in your coffee maker can lead to mineral deposits or scaling, potentially affecting the performance and lifespan of your machine.

As a best practice, empty the coffee maker’s water reservoir after each use, and clean the machine regularly to ensure it stays in good working condition and to maintain the best possible taste for your coffee.

How to Take Care of the Keurig Water Reservoir

Taking care of the Keurig water reservoir involves a few simple steps:

  • Regular Cleaning: Clean the reservoir at least once a week with mild soap and warm water. Rinse it thoroughly to ensure no soap residue remains.
  • Dry After Cleaning: After washing, allow the reservoir to dry completely before reassembling it back into the Keurig. This helps prevent mold and bacteria growth.
  • Empty When Not In Use: If you’re not going to use the Keurig for a few days, it’s best to empty the water reservoir to avoid stagnant water.
  • Use Filtered Water: To prevent mineral buildup, it’s recommended to use filtered or bottled water in the reservoir.
  • Descale Regularly: Over time, minerals in the water can build up in your Keurig, affecting its performance. Regularly descaling your machine according to the manufacturer’s instructions helps keep it in good condition.

With these steps, your Keurig water reservoir should stay clean, and your coffee will taste its best.

How to Clean Keurig Water Tank

Cleaning the Keurig water reservoir involves the following steps:

  1. Remove the Reservoir: Unplug your Keurig and take off the water reservoir. Make sure to also remove the lid.
  2. Rinse: Rinse it under warm water. Don’t use detergent or soap, as this can leave a residue and affect the taste of your coffee.
  3. Wipe Down: Wipe down the inside and outside of the reservoir with a soft, damp, non-abrasive cloth.
  4. Deep Clean (if necessary): If you see scaling or mineral build-up, you may need a deeper clean. Fill the reservoir with a solution of one part white vinegar to one part water. Let this soak for about four hours, then empty and rinse well to remove any vinegar residue.
  5. Dry and Reassemble: Allow the reservoir to dry thoroughly before placing it back in the machine.

For a deeper clean of the entire machine, Keurig recommends descaling every 3-6 months using Keurig’s descaling solution or a mixture of vinegar and water.

Always refer to your Keurig’s specific user manual for cleaning instructions, as certain models may have different requirements.

How to Remove Mold in Keurig Water Reservoir

If you suspect mold in your Keurig water reservoir, follow these steps to clean it thoroughly:

  1. Unplug and Disassemble: Unplug your Keurig machine and detach the water reservoir.
  2. Visual Inspection: Check for visible signs of mold. Mold can appear as dark or fuzzy spots.
  3. Cleaning Solution: Prepare a solution using one part white vinegar to one part warm water. White vinegar is a natural disinfectant that kills most molds.
  4. Soak: Fill the reservoir with the vinegar solution and let it sit for about half an hour. This will help kill any mold or bacteria present.
  5. Scrub: After soaking, use a scrub brush or a soft cloth to clean the reservoir thoroughly, paying extra attention to any areas where you saw mold. A toothbrush can be helpful for hard-to-reach areas.
  6. Rinse: Rinse the reservoir thoroughly with warm water to remove any remaining vinegar solution and dislodged mold.
  7. Dry: Allow the reservoir to air dry completely to prevent the growth of new mold. Ensure that the reservoir is completely dry before reattaching it to the Keurig machine.

Remember, to prevent mold growth in the future, always empty the water reservoir if you’re not planning to use the Keurig for a few days, and clean it regularly with vinegar.


In conclusion, it’s crucial to manage the water in your Keurig reservoir properly. To maintain your Keurig machine’s longevity and optimal function, avoid leaving water in the reservoir for more than 2-3 days. 

Regular cleaning and descaling are necessary to prevent bacteria and mold growth and ensure you always enjoy fresh, great-tasting coffee.

Leaving water overnight might not cause immediate harm, but it’s not generally recommended due to potential bacterial growth, taste impairment, and mineral buildup. 

By regularly emptying and cleaning your Keurig water reservoir, you’ll help your machine serve you the best coffee for years to come. It’s a small effort for a significant reward – a perfectly brewed cup of coffee every time.

Want to learn how to clean a coffee maker? Read this article

Photo of author


Tim Lee is, as you might have guessed the founder of He is a former barista and a professional web publisher. He has now combined his knowledge and expertise in both subjects to create
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