I'm happy to help clarify, RobinJ! Samsung does recommend turning off the water supply before replacing the filter as this releases some of the pressure and makes removing the filter easier. However, if you are unable to get to the water shut off, or even if you just don't want to, that's ok too. The filter housing seals automatically when the filter is removed, so it won't hurt the refrigerator to leave the water supply turned on. ^Jecca