Product review (4 stars): Water filter replacement schedule
For those complaining about the price and short time between filter changes, I too had the same concerns until research turned up this info from Samsung. The filter replacement isn't required unless you notice a decrease in water flow or ice production. I have followed this guide and now change my filter about every 15-18 months with no changes in water taste or ice clarity. Talk about saving a mint, I used to change it religiously at 6 months.
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Hope this helps and no you do not need to turn off the water supply to change the filter, just a towel to wipe up the approx. 2-3 tbls. of water that comes out from removing the old filter, but that happens whether you turn off the supply or not.