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A coffee maker is warm, damp and usually closed up between uses, which is a comfortable place for mold and mineral buildup. Cleaning it takes a few minutes a week and one longer session every few months. It makes the coffee taste better and helps the machine last.
Why It Matters
In its 2011 household germ study, the public health organization NSF International swabbed 30 locations in the homes of 22 volunteer families. The coffee maker reservoir ranked as the fifth germiest spot in the home, and yeast and mold were found in half of the reservoirs tested. The study was small, but the reason holds: a moist tank that rarely gets washed grows things.
The second problem is scale. Tap water leaves minerals behind every time it is heated. That chalky buildup narrows the water path, slows brewing and can keep the water from getting hot enough, which makes coffee taste weak or bitter.
Cleaning and Descaling Are Two Different Jobs
Cleaning removes coffee oils, residue and anything growing on surfaces you can reach. Soap and water do this.
Descaling dissolves mineral buildup inside the machine, where you cannot reach. This takes an acid, either a descaling solution or white vinegar.
Doing one does not replace the other.
After Every Use
Throw out the grounds or the used pod right away. Wash the carafe, brew basket and any removable lid in warm soapy water, or put them in the dishwasher if the manual says they are dishwasher safe. Leave the reservoir lid open so the inside can dry.
Once a Week
Empty the reservoir, wash it with warm soapy water, rinse well and let it air dry. Wipe the outside, the warming plate and the area around the brew head, where coffee splashes and dries.
Every 3 to 6 Months: Descale
Keurig recommends descaling every 3 to 6 months, or when the descale light comes on for models that have one. That range is a reasonable guide for most drip machines too. If you have hard water, lean toward the shorter end.
The general method for a drip coffee maker:
- Empty the machine and remove any water filter.
- Fill the reservoir with descaling solution mixed as directed, or with equal parts white vinegar and water.
- Run a brew cycle halfway, switch the machine off and let it sit for 30 minutes.
- Finish the cycle and pour out the liquid.
- Run two or three full cycles of plain water until there is no smell left.
Check your manual first. Some manufacturers want their own descaling solution used and advise against vinegar, and single-serve and espresso machines have their own steps. The manual’s method is the one that keeps your warranty intact.
Signs You Are Overdue
- Brewing takes noticeably longer than it used to.
- The coffee is not as hot.
- The machine is louder, or sputters and steams more.
- You see white, chalky deposits in the reservoir or on the warming plate.
- The coffee tastes bitter or flat with the same beans.
Frequently Asked Questions
Does filtered water help?
Yes. Filtered water carries fewer minerals, so scale builds more slowly. You will still need to descale, just less often.
Can I use bleach?
No. Bleach is hard to rinse out of the internal tubing and is not meant for this job. Use descaling solution or vinegar.
Is an espresso machine the same?
The idea is the same, but the steps differ, and many espresso machines also need backflushing. Follow the manual. Our guide to espresso machines for beginners covers what to look for in a first machine.
The Bottom Line
Wash the removable parts after each use, wash the reservoir weekly and descale every 3 to 6 months. If your machine is past saving, our picks for the best coffee makers under $100 are a good place to start.
Sources: NSF International: 2011 Household Germ Study (executive summary) and Keurig: descaling guidance.