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Input:
Question: How do you clean the built-up minerals on the top of the machine?  I'm sure it's inside too.
Document: In general, this machine makes great tasting coffee and is convenient for daily use. Mine developed a critical leak at the top of the trough after 10+ years of daily use. Kudos to Bunn for making such a long lasting machine.Before throwing the machine in the trash, my curiosity got the best of me and I decided to take the machine apart. I was shocked at the amount of disgusting scale that had built up over the past 10 years.
Being a "how does this work" kind of guy, I partially disassembled the unit and saw that the plastic casing at this junction point had failed and, well, that was it - time to buy a new one. I'm sure I'll have this one for another couple Presidential elections.
We have been using this model for the past 8 years and enjoyed every cup of coffee that it brewed.It developed a slow leak somewhere under the heating cylinder. This prompted us to replace itwith the exact model. I'm sure it will continue to brew a great cup of coffee for the next 8 years.
Just recently my wife noticed that the Bunn coffee maker was leaking when she poured in the water to make a pot of coffee. Today I took the time to inspect the coffee maker closely to locate the leak.I saw water come out of a small hole underneath the top assembly and behind the brew funnel. I took the top off to see inside where the leak was coming from.
This is the third  BUNN coffee maker we have purchased in 20+ years. This one is cheaply constructed by comparison. The top slants forward and the brewing cone and the carafe don't line up. The unit has also forced water over the filter section causing a large mess to clean up. BUNN still brews the best coffee and the quickest so what can one do?
I'm impatient, and the way the Bunn coffeemaker can brew a pot sure pleases me. My old Bunn that died had a separate plastic carafe to pour water in, while the glass carafe was in place on the warmer. This newer design has a lid operated valve that stops the brewing process until lowered. Means the new one only needs one carafe. But discovered the valve isn't quite good enough to allow pouring water the night before, expecting to drop it in the morning.
Unlike a home brewer, this machine is designed to keep the water inside hot all the time so you can have a fresh pot of coffee in three minutes. And believe me, this Bunn performs. I have a hot pot of coffee in UNDER two and a half minutes. In fact, these commercial brewers spew water into the filter basket with such speed that, if you notice your coffee is weak, use two filters to keep the hot water in your grounds longer.
I'm about to try something else. Perhaps the fact that it has plastic heads, or something else, but it's not a reliable machine.
It's a convenient and well built machine but I can't give more than 3 stars for what I consider to be a design flaw. Bunn really needs to stress the cleaning of the unit. Unfortunately, the premise of this design is to save you time by using the reservoir. Do not assume this is a low maintenance coffee maker - it must be cleaned on a very regular basis.Given the cleaning issue and the inherent energy usage, I strongly recommend theBUNN HG Phase Brew 8-Cup Home Coffee Brewer.
It is mostly plastic, but sturdy. I like the fact that it is lightweight and compact because it travels well. My only beef is that, to empty it in order to put it back into storage, you need to unscrew the output spout and turn the machine upside down. Water empties -- not from the filler on top -- but from the dispenser/spout. When upside down, picture a drinking fountain -- the water flows upward out of the dispensing hole.
Answer: I don't currently have that problem  here but at my previous residence I used vinegar to clean the top and the tool to scale the tank input  if you have very hard water you may want to use a filter.