How Long Can You Leave Water in a Coffee Maker?

How long is it okay to store water in a coffee maker? Many individuals choose to leave water in their coffee maker, eliminating the need to refill the water tank each time they brew coffee. With water and coffee grounds already in the device, the only step left is to simply press the brew button to get your coffee ready.

So, is it alright to leave the water in the coffee in this? The answer is yes. You can leave the water in the machine and it will not cause any issues. However, allowing the water to set in the machine for longer than 12 hours can cause some issues. In this article, we will discuss how long you can put the water in the reservoir and what happens when you leave it for a long time.

So, How Long Can You Leave Water in a Coffee Maker?

Leaving water in the coffee maker for a long period is a widespread practice amongst most households. The thing is you can leave the water for a few hours in the machine without any issues. You can even leave the water overnight without any problems. Typically, it is recommended not to keep the water in the coffee maker for more than 12 hours.

Sometimes you may put the water in the machine for much longer without any issues. But when you leave it for a few days at a row, it can be problematic. There can be a lot of negative consequences because of this. Keeping water in the coffee maker for a long time can accommodate bacteria growth, mineral buildup, staleness, and some other issues.

If you are confused about how long you should keep the water in the machine, then we will recommend you to keep it for around 12 hours. Allowing the water to stay more than that inside the machine increase the chances of the consequences. Note that some machines are advertised to keep the water around 4 hours in a row. If they don’t utilize any function to keep the water clean, it will be very bad for their health.

What Happens When You Leave Water for So Long?

There are several consequences of leaving the water for so long inside your coffee maker. As we mentioned earlier, it can accommodate bacteria growth and some other issues. Here, with so long, we mean leaving the water for more than 12 hours. Here is what happens when you do this:

Stale Water

Typically, the water stays fresh for a long time. As per HealthLine, your freshwater can become stale after around six months. So, if you leave the water for long hours, there is no chance of taste being altered by the water becoming stale. However, imagine you keep the water in the reservoir and go for a vacation, and make coffee after returning home. This will surely make the water stale. In such situations, make sure to change the water and use freshwater.

Bacteria Growth

Your machine can grow bacteria if you leave it for a long duration. Especially, when you leave the machine unattended for around 12 hours, it begins losing its pH gradually. This allows the bacteria to grow easily. Sometimes, this can cause alteration in the taste of the coffee.

However, note that it will take a lot of time for the bacteria growth. That means leaving the machine overnight shouldn’t cause this issue. However, if you frequently leave the water reservoir full, it can accumulate the growth of mold. Sometimes the mold can prevent the machine from working properly. Moreover, it might be mixed with the coffee when you try to make the coffee after a long time.

Mineral Deposits

The mineral deposits are pretty obvious in the coffee maker even if you don’t leave water in the reservoir. However, leaving the water for a long time frequently can quicker the growth of the minerals. In case you don’t know, the minerals consist of sodium, calcium, magnesium, and other substances. They are not harmful or toxic but they can significantly lower the performance of the device.

Such as, the minerals buildup inside the machine will prevent the heating element from producing enough heat. As a result, the machine may not be able to bring out the flavor from the coffee. Moreover, the machine will require more power as it will overwork to heat the water. This way the buildup can be bad for the machine. You can reduce the chances of buildup by keeping the machine clean and not allowing water to sit in the reservoir for 12 hours.

Can You Leave Water in a Keurig?

Typically the Kuerig coffee maker can hold around 40 to 80 ounces of water to make around 10 cups of coffee. As per the manufacturer, you can keep the water in the Keurig machine. However, if you leave the water for a long period in the machine, it will definitely accumulate lime and bacteria growth.

Especially, the bacteria love it dark and cold. This increases the chances of bacteria growth. As per a study of the University of Valencia, there can be some dangerous bacteria and mold grow inside the Keurig. There are chances of contamination of the bacteria in your water from the water reservoir and this will be bad for your health. These bacteria even included E. coli, which can be dangerous for the human body.

The problem is there is no way to drain the water from the Keurig machine. You might require dissembling the coffee maker if you want to remove the water from the device.


Your coffee maker can offer you a good and long-term performance when you utilize it in the right way. Besides, proper maintenance and cleaning are also very important to keep your coffee maker upright. It is unclear whether it is safe or not to leave water in the machine. However, we will recommend you to avoid leaving the water as there are chances of negative consequences.