It’s necessary to use a water filter here because the water out of the tap is contaminated water, not only isn’t it treated, but it harbors bacteria and viruses that could make us very sick. We have been through many water filters trying to find the best system for our family. We have been using our current system for three months and were told we needed to change the sediment filter every three months. Today we changed it and took a comparison photo of the new cartridge and the dirty one needing to be replaced. If you ever wonder why our “white” socks are more of a reddish dirty color, you will know because our laundry water is tap water. We are very thankful for water filters so we can drink clean water!