Hi Helen -
I guess the answer to a lot of questions with MAC is "It depends."
My home is highly unlikely to contain NTM in the water according to Dr Falkingham because we are plagued by pink slime mold. According to his research at the University of Virginia, the two cannot coexist in your pipes. As a result, I am probably less cautious than many people - we use .2 micron filtered drinking water for safety, keep our hot water heater at 138F to prevent growth of NTM, and use a rainfall (big drop) showerhead. Otherwise, my water precautions are minimal. I do use tap water for toothbrushing at home. But when we travel, we carry bottled spring water for drinking, toothbrushing, taking meds, etc.
This has worked for me for 4 years - 1 1/2 on the Big 3, 2 1/2 with airway clearance and nebulizing.
I'll answer your other question about saline in the other discussion.
Do you have any other questions about living with MAC?
Sue