Today's question: How is the water from my refrigerator door different from my tap water?
"Plain Talk" answer: Your refrigerator should be hooked up to your home's main water supply line, so it is receiving the same water as comes from the tap. However, refrigerator water goes through a point-of-use filter and is chilled in the refrigerator’s cooling compartment before being dispensed. As with any POU filter, check with the manufacturer to determine what elements are removed and how often the filter should be changed. If the filter isn't changed regularly, bacteria and other contaminants may build up in the refrigerator cooler.
For more information on this and many other water-related topics, check out "Plain Talk About Drinking Water" by Dr. James M. Symons.