I haven't hooked up to a freshwater supply yet. I usually stay at state parks and they usually have power but not water, it seems to always be the freshwater tank that I use. That's why I was considering the cold water side at the kitchen only. Another reason I was leaning that direction is to stretch the filter life, or is there a reason that I should filter everything that comes into the water system even when I fill the tank? I chlorinate the tank sometimes, that was another reason I wanted to filter the kitchen water.