How to Keep Bunn Coffee Maker Pot From Overflowing or Not Filling Up Far Enough by Adjusting the Water Level

Updated on June 6, 2018


This article works best for the Bunn CW Series coffee maker that has the brew water coming directly from a plumbed water source. In other words, your brewer has a water line that connects to your plumbing and draws that water from your plumbing.

The Bunn Coffee Brewer CW Series system is a terrific coffee unit.  When you start the brewer the water will run for a set period of time and then shut off automatically.  If the water pressure feeding into your coffee brewer is too high, you stand a chance of the coffee overflowing the pot before it automatically turns off.   If water pressure running into your coffee brewer is too low, you'll only have a half full pot of coffee when your water turns off.

This article will tell you how to adjust the water level on your Bunn CW series brewer.

If You Are Trying to Increase The Water Volume in the Brew Pot

If your water is not filling up far enough in your Bunn unit. Try these steps.

1. With the Bunn unit power unit turned on, not actively brewing but "On." Be sure there is an EMPTY coffee pot on the burner beneath the brewer to catch the water.

2. Look for the "Start" Switch. This is the black switch that is located toward the top of the front face of the unit.

3. Press down the black switch and hold it until three clicks are heard. The clicks are kind of like pulses that you'll feel and hear.

4. When you hear the clicks take your finger off the switch right away. (Holding the switch for more than a couple seconds AFTER the three clicks will start the whole process over)

5. After you release the switch, then press it down again. I'd suggest just pressing it once, maybe twice. Each time you press the button tells the brewer to let the coffee run into the pot for two more seconds.

6. Let the pot run. I suggest not using any coffee beans at this point. See how far the water rises in the pot. If it still is not rising far enough, repeat the process and add more seconds. I suggest doing this without coffee so you don't waste coffee on trial and error, plus it is easier clean up if it all spills over.

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If You Are Trying to Decrease the Amount of Water in the Coffee Pot

1. Make sure that the power to the brewer is on. Don't have it actively making a pot of coffee, just be sure the power is on like it normally is. Be sure there is an EMPTY coffee pot on the burner beneath the brewer to catch the water.

2. Locate the "Start" button. This button is black and is located toward the top of the front faceplate with other switches and a light on it.

3. Press the "Start" button once for every two seconds you want taken off the time the water will pour. Don't hold the button down long. If you want to take four seconds off the amount of time you want the water run, press the button twice (2 presses x 2 seconds = 4 less seconds of water running. The more times you press the "Start" button, the shorter the pouring time will get.

4. Once you are done choosing the amount of time you want to take off, press and hold the "Start" button down until you hear three clicks. (Note that this is the exact opposite of what you would do when increasing water pressure)

5. Then let a pot fill up so you can check the level. I'd suggest doing this without using coffee so you don't waste coffee during this trial and error process. Also, if the pot somehow overflows, water is less of a mess than coffee.

If None of the Above Seems to Be Working

If the steps above are not working, I think I know what else you have to do. Basically the coffee machine can be set up so that no one can adjust the water level. In other words, you can disable the water volume level controls. If you've had no luck, it is probably because the machine is set to not allow you to adjust the settings. There is a way to reverse this and enable yourself to adjust the settings.

I have to be honest here, I've never done this particular fix. Everything else you've read so far, I have done a lot of, except this. I just know it from speaking to a Bunn technician.

If you are not sure what you are doing here, call a professional or do it at your own risk.

This should enable the machine to allow you to adjust the settings Here's what I was told, but I've never done:

1) See the panel I have my hand on? Remove this panel by unscrewing the screws.

2) Look inside the machine. There should be a switch (or a 'microswitch' as the tech called it) on the lower right side.

If you are having problems it is likely that this switch is set to "Lock" or in the "Lock" position. If it is, change the switch to the "Set" position. This will allow you to set different water volume levels.

I hope that helps!

OK, What If Absolutely No Water Comes Out?

If no water is coming out of your Bunn coffee brewer there are any number of things that could be wrong that I have no idea how to fix. That said, there is one method that you definitely want to try before you start to hate your coffee machine. You simply might not have enough water in the reservoir tank. I wrote a very detailed article on how to get the water to come out of the brewer and into the pot.

It should help you to get that water flowing again.


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    • profile image


      4 weeks ago

      CWTF-15. Works great as a pour through. As soon as I connect a water line (even if power is off), water starts coming through the machine. With the top off so you can view the fill tray, water bubbles up out of the reservoir. I have replaced the solenoid valve, no change. Who has had this happen, and what is the solution? It seems to me that the only option I have not tried is to block the second water line in the back of the machine (the one from the reservoir, not the one that feeds through the solenoid).

    • profile image


      4 weeks ago

      Neat article

    • profile image


      2 months ago

      I have a Bunn dual coffee maker that has the hot water spicked on it and can’t get any water to come out. It’s brand new

    • profile image

      Jack watkins 

      2 months ago

      My bunn is not auto fill and my water level to low for the amount I add to make coffee how do I fix this?

    • profile image


      17 months ago

      How do I get the frequent adjustment light to go off

    • profile image


      21 months ago


    • profile image


      2 years ago

      Some notes from the Bunn manual that would be a useful addition here:


      CAUTION - Disconnect the power source from the brewer prior to the removal of any panel for the replacement

      or adjustment of any component.

      NOTE: Prior to setting or modifying batch sizes, check that the brewer is connected to water supply, the tank is

      properly filled, and a funnel and server are in place.

      1. Modifying batch sizes. To modify a batch volume, first check that the SET/LOCK switch is in the “SET” position

      on the circuit board.

      To increase a batch size. Press and hold the START or BREW switch until three clicks are heard. Release

      the switch (Failure to release the switch within two seconds after the third click causes the volume setting to

      be aborted and previous volume setting will remain in memory) and press it again one or more times. Each

      time the switch is pressed, two seconds are added to the brew time period. Allow the brew cycle to finish in

      order to verify that the desired volume has been achieved.

      To decrease a batch size. Press and release the START or BREW switch once for every two-second interval

      to be removed from the total brew time period; then immediately press and hold down the START or BREW

      switch until three clicks are heard. Release the switch. (Failure to release the switch within two seconds after

      the third click causes the volume setting to be aborted and previous volume setting will remain in memory).

      Allow the brew cycle to finish in order to verify that the desired volume has been achieved.

      Page 6

      2. Setting batch sizes. To set a batch volume, first check that the SET/LOCK switch is in the “SET” position on

      the circuit board. Press and hold the START or BREW switch until three distinct clicks are heard, and then

      release the switch. (Failure to release the switch within two seconds after the third click causes the volume

      setting to be aborted and previous volume setting will remain in memory). View the level of the liquid being

      dispensed. When the desired level is reached, turn the ON/OFF switch to “OFF”. The brewer remembers this

      volume and will continue to brew batches of this size until the volume setting procedure is repeated.

      NOTE: When brewing coffee, batch volumes will decrease due to absorption by the coffee grounds.

      3. Setting programming disable feature. If it becomes necessary to prevent anyone from changing brew times

      once programmed, you can set the SET/LOCK switch to the “LOCK” position. This will prevent any programming

      to be done until switch is once again placed in the “SET” position.

    • profile image

      karen walker 

      3 years ago

      We have a bunncoffee maker and some held the start button in for several minutes, now the water keeps flowing. is there anyway to reset the bun so it makes only one pot at a time. modle # CWTF2/2 Twin

    • profile image


      4 years ago


      We have a Bunn coffee maker at our church and seems we are getting grounds in the coffee because the grounds are reaching the top of the filter.

      Will adjusting the water flow help with this problem ?

      Any help is appreciated !

    • TurtleDog profile imageAUTHOR


      6 years ago

      You are so welcome Scott. Glad the coffee machine micro switch was aOK. Glad your coffee pot is full now. Thanks so much for stopping by

    • profile image


      6 years ago

      Thanks and the micro switch worked as described. It took me a few times to get it to the level i needed. I now have FULL pots of coffee!

    • TurtleDog profile imageAUTHOR


      6 years ago

      Both the reservoir on the ones with burner pots and the version (air pot) you are talking about has an interior burner that stays on all the time to keep the water in the reservoir hot.

      Thanks for the comment tina!

    • profile image


      6 years ago

      I'm thinking of purchasing a CW series unit that brews directly into an airpot. I was thinking this would be an energy saver in addition to not having the coffee evaporate away in a glass pot. However, it occurred to me that perhaps the resevoir of water always stays hot (has a burner element on). This would make it NOT more energy efficient. I can't find an answer anywhere online. Do you know? Does it stay hot all the time or just heat when you hit the brew button? Thanks for any help.

    • TurtleDog profile imageAUTHOR


      6 years ago

      Hi Douglas! Sounds like you either need to turn the timer way down so it turns off much sooner (which I'm guessing you tried after reading this post) or something needs to be replaced, which unfortunately I can not help you with here. Maybe your timer is bad. That said, come to think of it, the timer adjustment could still be your solution. Often if you work on the lines (replace them, clean then, get new plumbing, etc) it could affect the pressure of the water going into the unit in a good way. That is, the water flow becomes more efficient (faster, stronger) and the timer, still being adjusted to account for your 'old' line/plumbing, isn't adjusted properly to account for this. Reduce the timer (by referencing the section "Decrease the Amount of Water" above and try again.

      Thanks for commenting! Good luck!

    • profile image

      Douglas Mark Everitt 

      6 years ago

      The water was unhooked from the machine and when the new line was installed water just keeps pouring and does not shut off HELP !

    • TurtleDog profile imageAUTHOR


      7 years ago

      Good point Mark. I'd still suggest trying it first with coffee (after adjusting the level without coffee) first. I'm sort of talking on a limb here since I haven't had any problems but I suspect different coarseness or fineness of the grinds can retain more or less water. If it comes up short on your first 'real' pot of coffee then adjust a bit.

      Thanks for the comment! Appreciate it.

    • profile image


      7 years ago

      Hi thanks for the post it was a good start to fixing the machine, one think you might want to add is this: when you are adjusting the water level remember to add a bit more time. When I was not using coffee I set it to a perfect level, but then when I brewed my first pot it was way less, it was then when I realized that the coffee grounds soak up a fair bit of water, so I had to readjust it.


    • TurtleDog profile imageAUTHOR


      7 years ago

      Hi Marie! Thanks for the great, great comment! Well.. I guess a lot of things could be wrong with the brewer but I suspect that you are no filling it up far enough for water to dispense. I added a section to my post for this. Look to the section called "OK, What if Absolutely No Water is Coming Out" and click on the link "Click Here to Read This Article"

      The instructions might not be exactly right for your model but check it out. It might give you an idea of what to try in order to fix. Again, I think you might not be filling it enough. The article will explain this more.

      As far as heating the water up. I'm thinking if you leave it in there about 20 minutes that should do it for sure.

    • profile image


      8 years ago

      I just installed a new Bunn Machine yesterday and I have become familiar with adjusting the volume.

      The click is not really a click.

      It is the sound of the water pump pulsing on and then


      Release the button within 2 seconds of the third "pulse"

      Hope this helps.

    • TurtleDog profile imageAUTHOR


      8 years ago

      Hi! Thanks for the comment! Assuming you are doing everything correct above, you might not feel the click or thumping of the unit if you have a really old Bunn unit (though I'm not sure what constitutes 'old' but let's say 10 years for sake of it) or a non-bunn unit. Let's also assume this feature on coffee machine is not broken either..... on older models there is no clicking. You need to remove the thin metal wall or plate that sits just behind the coffee pot. It is held in by I believe 4 screws. There is a timer inside that you can adjust by hand. Honestly, it has been so long that I forget what the timer looks like :-) so you might need to do a little trial and error.

    • profile image


      8 years ago

      I don't feel the three clicks after I do the procedure


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