Check the back of the unit to see if it was installed with soft vinyl hose to the wall supply. If so, change it to copper or stainless to remove residual taste and odor issues. You may have to flush the water reservoir in the fridge afterward by running at least 2 quarts thru the door dispenser. Change the filter every 6 months.
The problem with using a filter is two-fold...on one hand, it removes chlorine and cysts from the water. On the other hand, the removal of chlorine allows the water standing in the 2-quart reservoir to be unprotected. It can stagnate if not used regularly, so run a glass or two every couple of days even if you give it to the dog.