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Why Does My Bunn Coffee Maker Overflow


Experiencing an overflow in your Bunn coffee maker can be a frustrating start to your day. Did you know that factors such as the grind size of your coffee beans or a poor seal on the basket could lead to this issue? This blog post will walk you through common causes and provide actionable solutions to prevent future overflows in your machine.

Read on for valuable tips to enjoy a seamless brewing experience!

Quick Takeaways
  • Excess ground coffee and finely ground coffee beans can cause a Bunn coffee maker to overflow. Use the recommended amount of grounds and consider adjusting the grind size to prevent clogging.
  • Poorly sealed baskets, incorrect filter usage, and high brew volume settings can also contribute to overflow issues in Bunn coffee makers. Ensure proper sealing, choose the right filter, and adjust the brew volume as needed.
  • Regularly checking and cleaning spray heads, resealing leaky gaskets, checking for hard water buildup, and inspecting/repairing broken pump valves are additional troubleshooting tips to prevent overflow problems.
  • By following these steps and taking preventative measures, you can enjoy a seamless brewing experience without worrying about messy overflows in your Bunn coffee maker.

Common Causes of Bunn Coffee Maker Overflow

Excess ground coffee, finely ground coffee beans, poorly sealed basket, type of filter used, and brew volume set too high can all contribute to your Bunn coffee maker overflowing.

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Excess ground coffee

Too much ground coffee can cause your Bunn coffee maker to overflow. This happens when you put more coffee than needed in the pot. It blocks the way out for water, causing it to back up and spill over.

You should use just enough grounds as per the machine’s guide. Using an excess amount can lead to a mess and even damage your machine in severe cases.

Finely ground coffee beans

Using finely ground coffee beans in your Bunn coffee maker can contribute to overflow issues. Finely ground coffee has a smaller particle size, which means that it can easily clog the filter and slow down water flow.

When the water cannot pass through the coffee grounds quickly enough, it can result in an overflow of water and grounds out of the brew basket.

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To prevent this problem, it’s important to adjust the grind size of your coffee beans. If you notice that your Bunn coffee maker is overflowing with finely ground coffee, try using a coarser grind instead.

This will allow for better water flow and help prevent blockages in the filter.

Poorly sealed basket

A poorly sealed basket can also lead to overflow issues in your Bunn coffee maker. If the brew basket isn’t properly sealed, water may leak out during the brewing process, causing a mess and potential overflow.

Make sure that the brew basket is securely closed before starting the brewing cycle to prevent any leaks or spills.

Type of filter used

The type of filter you use in your Bunn coffee maker can contribute to overflow issues. Filter paper or a highly dense filter can slow down the flow of water, causing it to splatter and overflow from the brew basket.

It’s important to choose a filter that allows water to pass through easily without clogging. Additionally, if the filter is not properly seated in the basket, it can lead to overflow problems.

Make sure the filter is securely fitted before brewing your coffee. Remember, using the right filter can help prevent overflow and ensure a smooth brewing process for your Bunn coffee maker.

Brew volume set too high

If you set the brew volume too high on your Bunn coffee maker, it can cause overflowing. When the machine tries to pour more water than it can handle, it ends up spilling over and making a mess.

To prevent this issue, make sure you adjust the brew volume to the correct level recommended for your specific model. By doing so, you’ll ensure that the right amount of water is used during each brewing cycle and avoid any unnecessary overflow problems.

Solutions for Preventing Bunn Coffee Maker Overflow

To prevent Bunn coffee maker overflow, you can adjust the grind size of your coffee beans, make sure the basket is properly sealed, use the correct filter, and adjust the brew volume to a lower setting if necessary.

Additionally, regularly checking and cleaning the spray heads can help ensure proper brewing without any overflow issues.

Adjusting grind size

To prevent your Bunn coffee maker from overflowing, you can adjust the grind size of your coffee beans. Here’s how:

  1. Use a coarser grind: Finely ground coffee beans can cause the brew basket to overflow. To avoid this, use a grinder or choose a coarser grind setting if you’re buying pre-ground coffee.
  2. Experiment with different grind sizes: If you find that your coffee maker still overflows even with a coarser grind, try adjusting the grind size slightly. Finding the right balance will help prevent overflow.
  3. Check the manufacturer’s recommendations: Some Bunn coffee makers have specific guidelines for grind size. Refer to the user manual or check the manufacturer’s website for recommended settings.
  4. Test and make adjustments: Start with a medium-coarse grind and brew a pot of coffee. If it overflows, gradually increase the grind size until you find a setting that prevents overflow.

Ensuring proper sealing of the basket

To prevent your Bunn coffee maker from overflowing, make sure the brew basket is sealed properly. Here are some tips to ensure a good seal:

  1. Check the position of the brew basket: Make sure it is aligned correctly with the coffee maker and fully seated in place.
  2. Inspect the gasket: Ensure that the gasket inside the brew basket and on the bottom of the sprayhead is clean, intact, and properly positioned.
  3. Clean any residue: Wipe away any coffee grounds or debris from the rim of the brew basket and where it connects to the coffee maker.
  4. Use correct filter size: Use a filter that fits snugly inside the brew basket without folding over or allowing gaps for coffee grounds to escape.
  5. Avoid overfilling: Don’t exceed the maximum recommended amount of ground coffee for your desired brew volume.
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Using the correct filter

To prevent your Bunn coffee maker from overflowing, it’s important to use the correct filter. Here are some tips:

  • Use a filter paper or a filter with medium density. Highly dense filters can slow down the water flow and cause overflow.
  • Make sure the filter is properly seated in the brew basket. If it’s not fitted correctly, water can bypass the coffee grounds and overflow.
  • Avoid using filters that are too large for your coffee maker. Oversized filters can lead to excessive water in the brew basket, resulting in overflow.
  • Consider using a flow restrictor sprayhead if your Bunn coffee maker has one installed. This can help regulate the water flow and prevent overflow issues.

Adjusting brew volume

To prevent your Bunn coffee maker from overflowing, you can adjust the brew volume. Here’s how:

  1. Check the water level in the reservoir before brewing. Make sure it’s at the correct level according to your machine’s instructions.
  2. If your coffee maker has a brew volume setting, adjust it to a lower level to reduce the chances of overflow.
  3. Experiment with different brew volumes to find the right balance between getting enough coffee and preventing overflow.
  4. Keep in mind that using too much water or too little can affect the strength and taste of your coffee, so make adjustments accordingly.
  5. Pay attention to any guidelines or recommendations provided by Bunn for adjusting the brew volume on your specific model.

Checking and cleaning spray heads

To prevent overflow in your Bunn coffee maker, don’t forget to check and clean the spray heads. Here’s what you need to do:

  1. Remove the brew basket and carafe from the coffee maker.
  2. Look for the spray heads, which are located above where the brew basket sits.
  3. Inspect the spray heads for any clogs or debris that may be blocking the water flow.
  4. Use a toothpick or a small brush to gently clean the spray heads and remove any buildup.
  5. Rinse the spray heads with clean water to ensure they are completely clear.
  6. Once cleaned, reassemble the coffee maker by placing the brew basket and carafe back in their positions.
  7. Run a brewing cycle with just water to flush out any remaining residue from cleaning.

Other Troubleshooting Tips for Bunn Coffee Maker Overflow

– Reseal any leaky gaskets to prevent excess water from escaping.

– Check for hard water buildup in the coffee maker and descale if necessary.

– Inspect and repair any broken pump valves that may be causing the overflow.

– Ensure that the carafe is properly removed during brewing to avoid spillage.

Resealing a leaky gasket

If you notice that your Bunn coffee maker is leaking from the bottom, it could be due to a leaky gasket. The gasket is a seal that prevents water from escaping, but over time it can become worn or damaged.

To reseal the gasket, you’ll need to disassemble the coffee maker and locate the gasket. Remove any debris or residue around the area and place a new gasket in its position. Make sure it fits snugly and securely before reassembling the coffee maker.

This should help prevent any further leaks and ensure your Bunn coffee maker functions properly.

Checking for hard water buildup

To prevent overflow in your Bunn coffee maker, it’s important to check for hard water buildup. Hard water contains minerals that can accumulate in the machine over time, causing clogs and reducing its efficiency.

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One way to check for this buildup is by examining the spray heads. If you notice any mineral deposits or blockages, you can clean them using a vinegar solution or a descaling product specifically designed for coffee makers.

Regularly checking and cleaning for hard water buildup will help ensure smooth operation and prevent overflow issues with your Bunn coffee maker.

Inspecting and repairing a broken pump valve

If your Bunn coffee maker is overflowing and you’ve already checked for excess ground coffee and a poorly sealed basket, it’s time to inspect and potentially repair the pump valve.

A broken pump valve can cause water to flow too quickly or not properly into the brew basket, resulting in an overflow. To inspect the pump valve, you will need to disassemble your coffee maker following the manufacturer’s instructions.

Look for any visible signs of damage or blockage in the pump valve area. If you notice any issues, such as cracks or debris blocking the flow, it may be necessary to replace or clean the pump valve.

Referencing Bunn’s troubleshooting guide can also provide specific instructions on how to repair a broken pump valve if needed.

Properly removing the carafe

To prevent overflow in your Bunn coffee maker, it’s important to properly remove the carafe. When you take out the carafe after brewing, make sure to do it slowly and carefully. Avoid jerking or tilting the carafe too much, as this can cause leftover coffee to spill over into the brew basket and create a mess.

By removing the carafe gently and smoothly, you can help maintain a clean brewing process and reduce the risk of overflow. Remember, taking small steps during this simple task can have a big impact on preventing coffee maker issues.


In conclusion, understanding the common causes of Bunn coffee maker overflow can help you prevent this issue from happening. By adjusting the grind size, ensuring proper sealing of the basket, using the correct filter, and adjusting brew volume, you can enjoy a spill-free brewing experience.

Remember to regularly check and clean spray heads, reseal leaky gaskets if necessary, and inspect for hard water buildup. With these troubleshooting tips in mind, you’ll have a properly functioning Bunn coffee maker that won’t overflow.

Happy brewing!

Could a Malfunctioning Coffee Maker Warmer Cause Overflow?

A bunn coffee maker warmer malfunction could potentially lead to an overflow. If the warmer fails to regulate the temperature properly, it may cause the coffee inside the pot to reach a boiling point. This excessive heat can create pressure and result in an overflow, making a mess and potentially causing damage to the coffee maker.


1. Why does my Bunn coffee maker overflow?

Your Bunn coffee maker might overflow due to common causes like a clogged valve pump, surplus coffee, faulty valve pump or excess water buildup in the coffee maker.

2. What could be causing my Bunn coffee maker to leak from the bottom?

A leaking bottom may occur due to incorrect brew volume, issues with your water softener or fine ground coffee causing overflow.

3. How can I prevent my Bunn Coffee Maker from overflowing?

Troubleshooting your Coffee maker overflow problem can include steps such as flushing the coffee maker or not allowing adjustments that cause it to make too much at once.

4. Can using bottled water instead of tap water cause overflowing in my Bunn Coffee Maker?

Yes, sometimes using bottled water or filtered water rather than tap water can lead to an overflow because of different mineral contents present in each type of liquid.

5. How do I fix an overflowing issue on my Bunn Coffee Maker?

Understanding what’s causing the overflow is key: It might be that grounds are clogging your machine or filters aren’t fitted right; these are just two out of many tips for avoiding overflows and fixing this issue.

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About the author


Samuel is a coffee lover and a writer. He's travelled extensively throughout Southeast Asia and has soaked up the sun, the culture, and of course - the coffee. He loves to write about his experiences, and he hopes to travel even more in the future.

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