Thanks to all of you who offered thoughts on this topic. I was actually researching for two places: my brother whose (desert location) well is alkaline and who has a number of gorgeous camelias, begonias and a few epiphyllums. He's the one who will be adding the filter system to the line going into his shadehouse. And my own well which is high in calcium and iron, and I am considering whether to look at filters. More likely I am going to collect rainwater from my roof into a tank. My project will be slowly developed over the next couple of years. Your suggestions and references have given me a number of places to look, and I appreciate your help. Marguerite English.