Building a new house, bought a Hach hardness and iron test kit. No iron detected in the water, hardness shows 8 gpg. The house has 3 full baths, right now it's just my wife and I, but will have guests visiting every once in a while, and a kid in the next year or two. I've tried reading and understanding the various sizing web sites, but am not sure what size I need. I've read that most companies size based on "size" versus cu ft of resin. Others say that I need to calculate my SFR, and go from there - but doesn't give any method to calculate the SFR. I'd like to get a Fleck 7000 series, as I think this will fit the bill for the size of our house, but not sure of how much resin / size I need. Can anyone help?