re: Drip Coffee Filter Drainage Issue

Don't be so sure... Depending on what type of filter you have in the fridge (i.e., a paper or other physical-style filter), it's really just removing any free particulates and maybe some odorous materials.

If you have particularly hard water (with high dissolved mineral content), most of your conventional water filters will do very little to remove these dissolved metals. However, if you heat this water, the minerals can settle out easily.

The simple test is to put some water in a very clean vessel to boil... see if there is any residue left. Most likely will be white residue, which probably is calcium.

It is a very common issue though... you can resolve it by using clean purchased water, or just by cleaning the coffee maker from time to time.