Why is my Bunn overflowing? We recently upgraded at the office from an old and cold Mr. Coffee 12-cup at work to an old but hot Bunn coffee maker. It is a 10-cup BX-B, and appears to have no damaged parts. However, when I brew coffee, it starts gurgling out of the top after the first thirty seconds of brewing.

After a taking-apart and cleaning of the basket and spray nozzle, the grind of the coffee was the first thing I tweaked. Initially it was slightly fine due to having been purchased for the colder pot. I got an appropriate auto-drip grind and it continued to overflow. I also tried a larger style of coffee filter to ensure it wasn't overflowing with grounds getting down into the spout. 


  After about thirty seconds of a weak stream through the basket, water backs up to the point where it starts spilling, along with grounds, from the top of the brewing basket (where it meets the head of the base).


What should I do to counteract this behavior? 


I can ask for a coarser grind from the local coffee shop if that would make a difference. 
If it is a matter for concern, we are on the ninth floor of a building. 
The taps in the building typically have signs of hard water. 


I really would prefer to not go back to the colder pot since it brews less flavorful coffee, requires an excess of grounds to keep it from being watery, and takes 12-15 minutes to brew.
If I understand your description, it sounds as if water is flowing into the basket more quickly than it is flowing out. This could require adjusting the nozzle feeding the basket or the dispenser on the basket; probably the former, from your description of how soon after brewing the problem starts. Is there any way to slow down the inflow?

According to the Bunn troubleshooting guide, it is also possible that the coffee is too finely ground, or that the filter is not as permeable as it should be - naturally, Bunn recommends you use their brand of filters, and if you aren't, that's an easy thing to try. They also suggest that the sprayhead may be missing (it could also just be loose), and that you avoid finely ground coffee, decaffeinated coffee, and soft water.