Thank you for this great info. It's very helpful to hear about reverse osmosis, and the criteria of the micron size. I have an estimate tomorrow with a company that does whole house filtration using reverse osmosis for drinking water, along with UV water filtration. I'm not sure if they'll know anything about NTM, but once I get the specs of their system, I'm hopeful I'll be able to figure it if that will help block NTM.