Descaling removes mineral buildup that slows water flow and weakens flavor

Descaling is a cleaning process that dissolves calcium and magnesium deposits left behind by tap water. Over time, these minerals accumulate inside your BUNN's heating tank and tubes, making the machine brew slower and producing weaker coffee. A BUNN coffee maker should be descaled every 100 to 150 brewing cycles—roughly every month or two for a home user—or whenever you notice the brew cycle taking longer than usual.

BUNN sells a descaling solution made specifically for their machines, but white vinegar works just as well and costs less. The process takes about 30 minutes and requires only the descaling liquid, water, and a container to catch the output. You do not need to take the machine apart.

Key Takeaways

  • Descale your BUNN every 100 to 150 brew cycles, or whenever brewing slows down noticeably.
  • Use either BUNN descaling solution or white vinegar mixed with water in a 1:1 ratio.
  • The descaling cycle takes about 15 minutes; let the machine sit for another 15 minutes before rinsing.
  • Run two full tanks of fresh water through the machine after descaling to flush out all vinegar or descaling solution.
  • If your BUNN has a bypass tube (a small tube running down the side of the water tank), remove it before descaling and reinstall it afterward.

What you need before you start

Gather these items before you begin: a container or carafe large enough to hold at least 10 cups of liquid (to catch the descaling solution as it runs through), your descaling solution or white vinegar, fresh water, and a clean cloth or paper towels. If your BUNN model has a bypass tube—a small plastic tube that runs down the inside of the water tank—you will need to remove it. Check your user manual or look inside the tank; the bypass tube is usually held in place by a clip or sits loosely in a slot.

Do not plug in the machine yet. Empty any remaining water or coffee from the tank and carafe, and make sure the carafe is in place under the brew head.

Step 1: Remove the bypass tube (if your model has one)

Open the top of your BUNN and look inside the water tank. If you see a small plastic tube running vertically down one side, that is the bypass tube. Gently pull it straight up or unclip it, depending on how your model secures it. Set it aside on a clean surface—you will reinstall it after descaling.

If your BUNN does not have a bypass tube, skip this step and move to Step 2.

Step 2: Fill the tank and turn on the machine

Fill the water tank with your descaling solution. If you are using white vinegar, mix it 1:1 with water—so for a full tank, use half vinegar and half water. If you are using BUNN descaling solution, follow the ratio printed on the bottle (usually one packet per full tank).

Plug in the machine and turn it on. The heating light will come on. Wait for it to turn off, which signals that the tank has reached brewing temperature. This usually takes 10 to 15 minutes. Do not start brewing yet.

Step 3: Run the descaling solution through the machine

Once the heating light turns off, place your large container under the brew head to catch the liquid. Press the brew button and let the descaling solution run through completely. This takes about 5 to 10 minutes. You will hear the machine working and see the solution drip into your container. Do not interrupt the cycle.

When the tank is empty and no more liquid comes out, the descaling cycle is complete. Turn off the machine and let it sit for 15 minutes. This resting time allows the descaling solution to work on stubborn mineral deposits inside the heating tank.

Step 4: Rinse with fresh water twice

After the 15-minute rest, fill the tank completely with fresh water. Turn the machine back on and wait for the heating light to turn off again. Once it does, place your container under the brew head and run a full brew cycle of plain water through the machine. Discard this water.

Repeat this process a second time: fill the tank with fresh water, wait for the heating light to turn off, and run another full brew cycle. This second rinse removes any remaining vinegar or descaling solution taste. If you used vinegar and the smell is still noticeable, run a third cycle of fresh water.

Step 5: Reinstall the bypass tube and test

If you removed a bypass tube in Step 1, reinstall it now. Push it straight down into its slot or clip it back into place, making sure it sits securely. The tube should be fully inserted and not loose.

Fill the tank with fresh water one more time, turn on the machine, and brew a full pot of water into your carafe. Smell and taste a small amount to confirm there is no vinegar taste remaining. If the water smells or tastes like vinegar, run one more fresh-water brew cycle. Once the water tastes clean, your BUNN is ready to brew coffee again.

Common mistakes that leave mineral deposits behind

The most common error is skipping the 15-minute rest period after the descaling solution runs through. The solution needs time to sit in the heating tank and dissolve mineral buildup; running it straight through and rinsing when ready reduces how much buildup actually dissolves. Set a timer for 15 minutes and wait.

Another frequent mistake is not rinsing thoroughly enough. If you run only one tank of fresh water through the machine, vinegar taste will linger in your coffee for days. Two full rinse cycles are the minimum; three is safer if you used vinegar. The third rinse takes only a few minutes and prevents complaints about sour-tasting coffee.

Forgetting to remove and reinstall the bypass tube can also cause problems. If the tube stays in place during descaling, the solution does not reach all parts of the heating system, and mineral deposits remain. Always check your manual to see whether your model has one, and remove it before you start.

Frequently Asked Questions

Can I use regular white vinegar instead of BUNN descaling solution?

Yes. White vinegar works just as well as commercial descaling solution for dissolving mineral deposits. Mix it 1:1 with water and follow the same steps. The only downside is that vinegar has a stronger smell, so you may need to run an extra rinse cycle to remove the taste completely. BUNN solution is odorless and may require fewer rinses, but both are effective.

How do I know if my BUNN needs descaling?

The clearest sign is a slower brew cycle. If your BUNN normally brews a full pot in 3 to 4 minutes but now takes 5 to 6 minutes, mineral buildup is restricting water flow. You may also notice weaker coffee flavor or see white or tan crusty deposits inside the tank. Descaling every 100 to 150 brew cycles prevents these problems before they start.

What happens if I don't descale my BUNN?

Mineral deposits will continue to accumulate, slowing the brew cycle further and eventually clogging the heating tank. The machine may stop heating water properly or stop brewing altogether. Descaling is much easier than paying for repairs, and it takes only 30 minutes.

Can I descale a BUNN that is still under warranty?

Yes. Descaling is regular maintenance and does not void your warranty. In fact, BUNN recommends descaling in their user manual. Failing to descale and then having mineral buildup damage the machine is not covered under warranty, so descaling protects your investment.

Is it safe to drink the water that comes out during descaling?

No. Do not drink the descaling solution or the first rinse water. The solution contains concentrated minerals and vinegar or descaling chemicals. Always discard the liquid that runs through during the descaling cycle and the first rinse cycle. The water is safe to pour down the drain.