This phenomenon is actually well known. It's the reason for the military tradition of never washing coffee pots and mugs, too.
It's also why baristas leave the grounds in espresso machines until it is time to make a new cup. The coffee picks up the metallic taste if you clean it every time, but used grounds are good at preventing it. So, leave the grounds in until ready to brew (assuming it will be soon - you don't want to do that overnight.)
If you don't believe me, try it - go for a day or three only rinsing the pot or cup well (and with a cup, thoroughly wiping the rim clean), but not washing it with soap. You're putting 200 degree water in it so don't worry about sanitation - just rinse it very well. You will notice the taste change, and for the better.
http://www.navyhistory.org/2013/11/dont-wash-that-coffee-mug/
http://arstechnica.com/civis/viewtopic.php?f=23&t=546354
It's also why baristas leave the grounds in espresso machines until it is time to make a new cup. The coffee picks up the metallic taste if you clean it every time, but used grounds are good at preventing it. So, leave the grounds in until ready to brew (assuming it will be soon - you don't want to do that overnight.)
If you don't believe me, try it - go for a day or three only rinsing the pot or cup well (and with a cup, thoroughly wiping the rim clean), but not washing it with soap. You're putting 200 degree water in it so don't worry about sanitation - just rinse it very well. You will notice the taste change, and for the better.
http://www.navyhistory.org/2013/11/dont-wash-that-coffee-mug/
http://arstechnica.com/civis/viewtopic.php?f=23&t=546354
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