I have not really noticed anything...The pre filter, I just replaced and it was caked with a dark sediment so I guess its doing its job. Im just wondering if over time that however this thing works will it cause restrictions in my water flow? I assume it collects something from the water somehow, but it has no backwash...so it has to plug up eventually. The plumber who was out to my house said they are useless...period, end of story. It was here when I moved in, and I can see they are expensive to buy...would I buy one, probably not. Just wondering what others think of them?