Rule 1
Rule 1 is simple---it is not what you need to buy for your Longevity as much as it is what you need to stop buying, stop drinking and eating.
Since water is dirty and in the top 3 reasons for premature death-- $$$ is required to cleanse your water supply. For most a $120 tabletop water distiller works just fine for a couple.
Once you solve Rule 1, you could extend that to your bath / shower water, it is doable, but 99+% will not bother. City water has allot of problems even if you never drink it and just flush your toilet with it or wash your cloths with it---so that creates a larger problem and whole home water distillers exist, but 99.999% will never do that.
Once you have clean water that is just water, then you can drink that or use it to make yummy teas.
The odds are, you have never known a fellow human that has drank true water; not even a good water distiller can make true water. When a factory lab buys true water, it comes in 1 gallon thick / brown glass water jugs. A few people will use special water distillers and double distill-- that is not needed, because the air is super dirty, filled with heavy metals. Dealing with dirty air is out of human control and a clean house and clean bedroom essential.....sleeping with a water type air cleaner with plenty of wild oregano oil in the clean water- can do wonders. Otherwise, germ/chemical warfare affects the entire planet since 1949.