Here is what I know. I use a Keurig 1 cup coffee maker. I buy Tim Hortons Original Blend, medium roast ground coffee, at Target. I have an under the kitchen sink, a cold tap water filter, using a Pentair Carbon Filter Cartridge, TSGAC-10. The filter is designed to reduce Chlorine Taste and Odor and reduce Lime and Scale.
Our Kitchen Cold Tap water is the best tasting, is excellent for cooking, and makes the best tasting coffee. I also use a Thermos SS 10oz cup, for my daily coffee. There's NO metal taste. lol
This is my story and I stand behind it!