Do Coffee Makers Produce Bacteria in Water Reservoir?


Any warm, moist environment can promote the growth of bacteria. The kitchen has more bacteria than any other room in the house and coffee makers are not immune to bacterial growth.


  • The coffee maker's water reservoir is filled with fresh, clean water every time the machine is used, which tends to flush out bacteria. This water, however, is not heated until it leaves the reservoir, so there is no heat sterilization of the reservoir itself.

Food Source

  • Most bacteria need a food source to multiply. Although the reservoir is filled with water only, contamination in the form of stray coffee grounds or food crumbs may allow bacteria to grow rapidly.


  • Many types of bacteria form biofilms, thin layers of organisms adhering to a surface. The water reservoir is a likely candidate for bacterial biofilm formation because it is always moist.


  • Frequent cleaning of the coffee maker can reduce the growth of bacteria inside the machine. Experts recommend vinegar because it inhibits some bacteria, as well as many molds, and is nontoxic.

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  • Photo Credit Closeup of white coffee cup next to coffee machine image by Olena Talberg from
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