The lfs is in town, I live in the country and have well water that I think is tapped into some wasteland on the other side of the world. The lfs said (so did the ro/di guys I had come out and test the water) that our area has some really bad ground water for some reason. They were testing 1700 tds. My friend who live 10 miles away has 200 tds straight from the well, go figure.