Actually, the E145 has a galley "tank/jug" reservoir that is filled manually by the FA with bottled water. If you look along the wall in the aisle next to the galley, there is a compartment door. Inside that door is a tank which slides out into the aisle and is filled by the FA. Most of the time this is done before passenger boarding so they never see it. The coffee maker water on the E145 comes from bottled water and not the potable water system.