Thank you Russ. That was the most complete answer I could have ever expected. You took the time to not only read but understand what I wrote. I now understand my system better than ever. You are correct about the GAC filter being last. I had no idea that it can ADD solids. I was impressed by your prices, checked em about 3 days back, IF I decide to give it another try (probably not until after the holidays) I'll bring the entire unit by and get all new cartridges from you.