I agree with MtM, Mmsg, and this post is also for Denise and Phyllis,
I also drink tap water. I used to drink a lot of Perrier but it is my opinion that drinking so much water is unnecessary and just flushes out the water soluble vitamins like B's and C that can protect the CNS in addition to magnesium. Too expensive to keep replacing. I use the warm/hot tap water to make my ginger, turmeric and cayenne "tea". I use cold tap water to make orange juice (from concentrate) and coffee or tea. I dissolve my magnesium powder in tap water or orange juice. I read that the neurodegenerative diseases are associated with inflammation. MSG causes inflammation and hidden sources are difficult to avoid in the infiltration of voluminous hidden sources. Turmeric and ginger are both reported to reduce inflammation and even fight cancer. Several years ago pubmed.gov had reports of turmeric dissolving and possibly preventing the amyloid plaque forming in the brains of laboratory animals. I haven't researched any more because I felt I was improving on what I had learned and trying to get on with my life, taking care of my husband and trying to help others when asked if I have the opportunity.
As I mentioned, I am 70 and have been taking turmeric and ginger for several years and making earnest attempts to avoid hidden sources of MSG. My short term memory is better and my mind seems clearer. I am just s-l-o-w due to multiple head & neck injuries and dealing with a severed GI tract lining.