Just to be clear, we only use water from our purifier or bottled and haven’t sanitized our tank for at least the 5 years we’ve had it, and never drain the tank on purpose.
I always have used my 3-Stage filter and Softener system that filters down to .5 micron, which is good for almost all bacteria.
What I CAN TELL you, however, is that I’ve known of one coach owner who had a horrific stinch throughout his coach that they couldn’t kill despite how many waste tank treatments. FINALLY, they sanitized their fresh tank and…yup…problem solved!
So, whether or not your DRINK from your fresh tank is despite the problem of getting bacteria in there and having it set up shop. So, I’m a believer in filtration before any water gets into your tank if, for nothing else, smell.
And, one last consideration…DON’T FORGET ABOUT YOUR CLOTHES WASHER AND DISHWASHER needing clean water to use!