First, you are right Dr. Joe Falkinham does say they have tested spring water and found it safe. He is my go-to-guy on matters of water, studying it is his career.

Remember that the hosts on most web-based chats (like the mentors here on Mayo Connect) are not necessarily medical or scientific professionals. They are volunteers who have done a lot of reading and research (like me), so can be a helpful source of information. Every commenter filters 😉 the information they read through their own brain full of knowledge, experience, perception, values and opinions.

Let me give you a pertinent example. It is very difficult for me to engage in discussions about water I occasionally sip from a bottle, or the put ice in my drinks in a restaurant. MY brain does not believe that kind of incidental exposure to NTM/MAC is a high risk. But I may have a higher "risk acceptance" than other people, so I try to step carefully. However, I do pay attention to the water in my home, where I use it all day every day.

Having a host suggest that one check to see if a bottler is using reverse osmosis, which does not remove NTM, is the opposite of good information one would hope to receive in a chat. See this article:
"Reverse osmosis(RO) filters and granular activated carbon (GAC) filters, which are often used to remove chemicals from potable water, adsorb nutrient materials and may provide a means through which NTMs can multiply to infectious levels." https://cfpub.epa.gov/si/si_public_record_Report.cfm?Lab=NERL&dirEntryID=18293#:

I have never sat in on one of the socials in that group, but may do so just to get a feeling for the quality of the advice. Have you found them helpful on other issues?
Sue