Empty and rinse the reservoir weekly

The water reservoir is where mineral buildup and mold grow fastest. Empty it completely at least once a week, even if there is still water inside. Stale water sitting in a dark plastic tank becomes a breeding ground for bacteria and mold within days.

Rinse the empty reservoir under running water, using your fingers or a soft brush to wipe the interior walls. Pay attention to the bottom corners where sediment collects. If you see white, gray, or black spots, those are mineral deposits or mold — scrub them with a damp cloth or soft-bristled brush until they come off.

Dry the reservoir completely with a clean cloth before refilling. Leaving it wet overnight invites mold to return.

Key Takeaways

  • Empty and rinse your reservoir every week to prevent mold and mineral buildup from taking hold.
  • White crusty deposits are minerals from hard water; remove them with a soft brush or cloth and vinegar solution.
  • Run a vinegar-and-water cycle through the full machine monthly to dissolve mineral deposits inside the heating element and tubes.
  • Replace the reservoir if cracks appear or if mold returns after cleaning, because cracks trap water and bacteria.

Use vinegar to dissolve mineral deposits

If the reservoir has white, crusty buildup that does not come off with water alone, fill it halfway with white vinegar and let it sit for 15 to 30 minutes. The acid in vinegar dissolves mineral deposits without scratching plastic. Scrub gently with a soft brush, then rinse thoroughly with fresh water several times until the vinegar smell is gone.

For stubborn deposits, make a paste of equal parts vinegar and baking soda, explore it to the affected spots, and let it sit for 10 minutes before scrubbing. Rinse well afterward.

Run a vinegar cycle through the whole machine monthly

Cleaning just the reservoir is not enough. Minerals also build up inside the heating element, tubes, and spray head where you cannot reach them by hand. Once a month, fill the reservoir with a 50-50 mix of white vinegar and water, place an empty mug or carafe under the brew outlet, and run the machine as if you were making coffee.

Let the vinegar solution run until the reservoir is empty. Then fill the reservoir with fresh water only and run another full cycle to rinse out the vinegar. Repeat the water cycle one more time. This removes mineral deposits from the internal parts and keeps the coffee tasting clean.

If your water is very hard (you can tell by heavy white buildup on the reservoir), do this vinegar cycle every two weeks instead of monthly.

Check the water inlet tube for clogs

The tube that draws water from the reservoir into the machine can become clogged with mineral deposits or mold. If your coffee maker suddenly brews slowly or not at all, the inlet tube may be blocked.

Look at where the tube connects to the bottom of the reservoir. If you see white buildup around the connection, soak the reservoir in a vinegar-and-water solution for 30 minutes, then use a small brush or pipe cleaner to gently clear the tube opening. Do not force anything into the tube, as you can crack it.

If the tube is cracked or the clog will not clear, the reservoir may need to be replaced. Most coffee maker manufacturers sell replacement reservoirs separately.

Dry the reservoir completely before storing

Moisture left in the reservoir between uses is the main reason mold returns. After rinsing, stand the reservoir upside down on a clean cloth or drying rack so air can circulate inside. Leave it to air-dry for at least an hour before putting it back in the machine.

If you store your coffee maker for more than a week without using it, remove the reservoir, empty it completely, and let it dry fully before storage. Mold can develop in just a few days if water sits in a sealed, dark space.

Replace the reservoir if it cracks or discolors

Plastic reservoirs wear out over time. Cracks, even small ones, trap water inside where mold grows and you cannot clean it out. Permanent dark stains or discoloration that does not come off with vinegar and scrubbing also mean the plastic has absorbed bacteria or mold spores.

Replacement reservoirs are inexpensive — usually between $15 and $40 depending on the coffee maker brand — and are sold through the manufacturer's website or major retailers. Replacing a worn reservoir is cheaper than replacing the whole machine and ensures your water stays clean.

Frequently Asked Questions

Can I put the reservoir in the dishwasher?

Check your coffee maker's manual first. Many plastic reservoirs are dishwasher-safe on the top rack, but some are not. Hand washing with warm soapy water and a soft brush is always safe and takes only a few minutes. If the manual says the reservoir is dishwasher-safe, use the top rack and skip the heated dry cycle.

What does black mold in the reservoir look like?

Black mold appears as small dark spots or patches, usually on the bottom or sides of the reservoir where water pools. It may also look like a thin dark film. If you see black spots, soak the reservoir in a vinegar-and-water solution for 30 minutes, scrub with a soft brush, and rinse thoroughly. If the mold returns within a week, replace the reservoir.

How do I know if my water is hard?

Hard water leaves white, chalky mineral deposits on the reservoir and inside the machine. If you see heavy white buildup after just a few weeks of use, your water is hard. You can also buy an inexpensive water hardness test strip at a hardware store. Hard water requires more frequent vinegar cleaning — every two weeks instead of monthly.

Can I use bottled water in the reservoir instead of tap water?

Yes. Bottled water has fewer minerals than most tap water, so it will reduce buildup in the reservoir and machine. However, you still need to empty and rinse the reservoir weekly, because mold can grow in any standing water regardless of mineral content.