Why Does My Bunn Coffee Maker Overflow?

Although Bunn coffee makers are great and make flavourful coffee, every once in a while, a user will encounter the problem of their coffee maker leaking. This is a common incident that can happen for a variety of reasons and can be fixed.

So, the common question is, “Why does my Bunn coffee maker overflow?” In this article, we’ll look at the reasons that can cause either water or coffee to leak and also see what you can do to fix it so that your coffee isn’t ruined.

Why Is the Bunn Coffee Maker Overflowing a Problem?

If a Bunn coffee maker is overflowing, water or coffee will leak out. The water and coffee are at very high temperatures, so in addition to making a mess on your table, it possesses a safety hazard. You can easily burn yourself if you accidentally touch the leak.

The water leaking out can also seep into the parts of your Bunn coffee maker, which can damage it. It can also affect the taste of your coffee since the water can seep in. Leaking coffee can also stain your coffee maker and the surroundings and can be difficult to clean up.

So as you can see, if your Bunn coffee maker overflows, it can be quite problematic. You will need to quickly turn it off and then check what is causing the problems.

What Can Cause a Bunn Coffee Maker to Overflow?

A Bunn coffee maker can overflow for a few reasons, which can result in water or coffee leaking. Some of these reasons are listed below:

1. Coffee Used

Some types of coffee grounds can cause your coffee maker to overflow. If the consistency is not right, you’ll find that the water doesn’t properly pass through the grounds in the filter, and this will cause water to build up and start overflowing.

This can also happen if you don’t ground the coffee beans properly and evenly spread them before putting them into the filter. This can cause coffee to spill out of your coffee maker, which can be messy.

Typically, you should avoid low-quality coffee grounds as it is frequently seen to be the reason for Bunn coffee maker grounds spillover.

2. Unclean or Clogged Filter

The filter is the part that the water must pass through. If it is clogged from the coffee residue, the water might get blocked and start swelling up. Since the coffee grounds are also present there, they can mix and then spillover.

This issue can also happen for old or defective filters. The mesh in the filter can get blocked, so water or coffee will get stuck. Second-hand filters can often cause problems after some use.

3. Uncontrolled Flow Rate

Sometimes the reason your coffee maker is overflowing is that the flow rate of the water is not adjusted properly. If the flow rate of the water is too high, it will swell up in the filter instead of going through it and overflowing.

Though this is a rare issue in the Bunn coffee maker, it can happen from time to time. If you tend to configure the settings on your Bunn coffee maker, you can encounter this issue if you’re not careful.

4. Lime Scale Build Up

Coffee residue can easily stick to the coffee maker and eventually build up. In addition to contamination, the limescale build-up can interfere with the flow of your coffee or water. Large-scale limescale build-up can cause blockages in the Bunn coffee maker, further exacerbating the problem.

If you don’t regularly clean or descale your Bunn coffee maker, this can be a major cause for overflowing or spillages. It can also lead to damaging the item and reducing the life span.

Now, if you happen to find small lingering stenches of coffee in your coffee maker, you might want to take it apart and properly clean it.

5. Outlet Mismatch

Sometimes a mismatch in the outlet can cause water to swell and start leaking. If the outlet happens to be smaller than the inlet, overflowing can be a common occurrence. Either the rate of water must be adjusted according, or the outlet changed to match the size of the inlet.

6. Impure Water Is Used

The water used is also important. Water with some signs of hardness can cause overflowing in your Bunn coffee maker. Check your water supply for any signs of impurity as they can affect the flow rate and internal mechanism of your machine. Use clean water and make sure there are no signs of hardness.

7. Coffee Maker Can’t Handle the Amount to Be Brewed

Not all models are the same. Sometimes the amount of coffee added is too much for the maker, which can cause it to overflow. It is recommended to make coffee in smaller amounts if your model cannot handle it.

Fixing the Overflowing Issue

As you can see, there are many reasons why your coffee maker can overflow. As a result, there are many troubleshooting methods you can attempt to make the overflowing stop. It is recommended to try out each of these methods if the problem tends to persist.

1. Cleaning Your Bunn Coffee Maker

Limescale build-up and coffee residue can clog the internal parts of your Bunn coffee maker. When the coffee or water does not have a proper passage, it will start to leak out from the sides. So properly cleaning and doing maintenance on your machine is important if you don’t want it to overflow.

Daily maintenance usually consists of simply cleaning the coffee stains and washing the machine. It is recommended to perform a descaling operation once every month. You should do this more times if your water supply has some hardness.

For descaling or de-limbing, you can get a descaling tool. Take our machine apart and insert it into the parts and wash it properly. Remember to rinse it properly with warm water and then have the parts dry before putting them together.

Washing your coffee maker will make sure the passages are clear and will ensure a longer life. Remember to properly rinse the parts to remove any minute traces, or your coffee might taste unpleasant.

2. Changing out the Filter

A clogged filter can cause water to leak out of the sides. The filter is one of the most important parts of your Bunn coffee maker, and you should regularly clean it to remove coffee residue. Coffee residue can block holes in the mesh and prevent your coffee from properly mixing.

There also times when changing out the filter will prove to be the solution. If the filter is defective, you need to switch it out. You can try out different filters and see if that solves your overflowing problem. If you don’t regularly clean your Bunn coffee maker’s filter, you might have to replace it faster.

This is a common problem for paper filters as the filter can be folded improperly and thus affect the flow of water. It is recommended to check the paper filter after every use. Rinse it and then have it completely open before inserting it back into the machine.

3. Using Different Coffee

Sometimes, it can be the type of coffee beans or grounds your using that is causing your Bunn coffee maker to leak water or coffee. Check the consistency of your coffee grounds by taking a bit of it in a cup and then passing water through it. If the consistency is off, then the water will swell.

Although coffee grounds being the cause of overflowing are not common, it is still worth checking to see if they cause problems or not.

Sometimes the problem can also happen if you don’t tamper or spread the coffee grounds evenly. The grounds being concentrated in one space can cause small leaks, so always be sure to evenly spread them out before placing them on the filter.

There is also the issue that sometimes the amount of coffee grounds or beans used is too much for the particular model. You can use fewer grounds and check to see if the overflowing persists or not. If the grounds are thick, it will be better to use less of it as the coffee will be much more concentrated.

Try to use medium ground coffee if possible. It is the safest option as it prevents overflowing and prevents any sort of leakage.

4. Changing the Water Used

Try to always use clear and pure water. Impurities in the water can also enter the coffee machine and start building up inside it. If your water supply has signs of hardness, you might want to try out a different supply of water and notice the difference for yourself.

Hard water can also affect the taste of your coffee. So overall, it is much more beneficial to use purer water for your coffee maker. You can test this by simply passing only water through the filter and seeing if it fully passes through or not. If there are some impurities in the water,they will get stuck in the filter.

5. Adjusting the Flow Rate

One issue that some models have is that the flow rate of water is too high, which ends up causing it to leak sideways. First, you should look at the spray head to ensure it is working properly or not. Make sure that it is not loose, or water might spill out from there.

If you see the Bunn coffee maker leaking water from the spray head, you should check to see if it is damaged or not. In case the spray head is damaged, you will quickly need to replace it with an appropriate one.

You should also look over your settings. Try to set the coffee maker to brew slowly if you don’t have it set beforehand. Having the machine brew slower reduces the chances of overflowing.


We hope that this article has proven to be helpful in answering why does my Bunn coffee maker overflow. Although this is a common problem, it can be a bit annoying, and you will need to properly look through the issues to ensure a complete fix.

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