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elbanditoroso's avatar

Bacterial growth in standing water in a coffee maker?

Asked by elbanditoroso (22398points) January 14th, 2012

I use a Keurig coffee maker – the kind that has a water tank that holds 1.5 liters (approx.). When it makes a cup of coffee, it then draws in another 6–8 ounces from the water tank into the heating tank so that it always has boiling water ready for coffee.

Based on my coffee consumption, I have to fill the 1.5 liter tank every couple of days. So there is always water in the tank; sometimes it has been sitting there for 2–3 days before it empties and I have to refill the tank.

What, if any, risk is there of bacterial contamination in that tank on the 2nd or 3rd day? (yes, the tank has a plastic cover, but the tank has some openings at the top and bacterial are very small). Am I better off running a thin water line from my kitchen faucet to the bank of the Keurig and only filling it enough to make today’s coffee?

Or am I overthinking this?

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10 Answers

john65pennington's avatar

Surely, the makes of the coffee pot thought this out before placing it for sale on the market.

To be safe, we clean our coffee maker once a week with water and vinegar. Our pot does not hold water as yours, but if you have not been harmed by this coffee maker’s water procedure, I would not worry about it.

In the past, we owned a coffee maker that was attached to our water system. Like yours, it would hold hot water at the standby, just so a hot cup of coffee could be made within a few minutes. We suffered no ill effects from owning that coffemaker for 6 years.

DrBill's avatar

If the temp is near boiling that will prevent nastiness from growing in there

HungryGuy's avatar

Two to three days shouldn’t cause bacterial growth in what was originally clean water, but it won’t taste “fresh” any more and will affect the taste of the coffee.

Boiling it often will certainly kill any bacteria lurking in it, but again, it won’t taste fresh after a few days.

If’n I were you, I’d rinse it out each use, and then run a cycle with white vinegar once every couple of weeks.

Stinley's avatar

I think if you are replacing it regularly, every three days as you say, you will be fine. I have a coffee machine that has a tank for frothing and espresso (get me…) but use that bit rarely so always empty it and put clean water in

Zaku's avatar

Any bacteria in the water reservoir would pretty much all die when the water boils.

Also, your body is brimming with bacteria. If you somehow killed off the bacteria in your body, you’d probably die. Not all bacteria is bad.

Also, how does your percolator work? Is the water all evaporated and condensed before going into the pot anyway? I don’t think bacteria would not only survive the boiling but paraglide with the steam into your pot.

InkyAnn's avatar

@elbanditoroso I have a Keurig also, I love it! I have wondered this same question too since it seems like we drink about the same amount. Thank you for asking. That aside, I will leave water in its tank for no more than 2 days (the day I filled it and the fallowing day). They say that with it pulls the water from the tank and heats it, that it will be fine. But I just dont want to take the chance. I have animals in the house and the S/O is always working in the garage so I worry more about what could get in there from them than bacteria just forming from the water being stagnant.

elbanditoroso's avatar

@inky, that’s just it – is it worth taking the chance.

I imagine that the other answerers are most likely correct – the water will be boiled and kill anything anyway, but it comes down to a weighing of the risks.

Thanks for the comment.

InkyAnn's avatar

@elbanditoroso No prob ^_^. I think we should just put enough in for how ever many cups we are going to have that day. Most likely our safest bet all around.

fizzbanger's avatar

I wondered the same thing. I empty it out often, and descale it once a month.

Debwin's avatar

But does the water in your machine get boiled or does it just get real hot? Is that stagnant water just being warmed up?

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