Few things today are more laughable, or depressingly ironic, than the American embrace of a product like FIJI Water:
Spent the early portion of my professional life as a ground water engineer. I licensed several water bottling facilities. FWIW I drink tap water.
I fill my boat tanks with tap water. I fill my small water bottle with tap water.
Contrary to the hype posted earlier, chlorine in drinking water isn't deadly, there aren't regular mass poisonings from municipal systems, and I believe the odds favor a system that is checked multiple times daily for quality and safety (US municipal systems) under the EPA Clean Water Act standards over a loosely regulated "food" like bottled water which is under FDA jurisdiction.
Again, to each their own. If someone is afraid of their water system and they sleep better at night drinking from plastic bottles, have at it. Fear of the municipal system in the US are unwarranted. There have been times when standards were exceeded, or when people were made ill from the water. Water engineers and scientists don't wait for people to get ill before jumping into action to stop the carnage before the death toll mounts.
There have been areas with boil notices. These are news worthy events precisely because they are RARE. There haven't been epidemic, or large scale outbreaks of waterborne illness and disease in the US as unfortunately witnessed elsewhere in the world. One of the things I treasure about living in the US (and I have travelled to many places where this isn't true) is that anyone can enter a public space or building and have access to safe, clean, drinking water. No fee, no fine, no boiling, no need to fear cholera, giardia, crypto, or any other nasty bugs. The water from the tap has come from a system with continuos monitoring, testing, and adjustment of the system to ensure safety.
As for those not knowing what is in their fresh water tanks. Well, what can i say. You should know that your system is clean and safe even if that means installing a clean out port. I bet you wouldn't store your food in a dirty old metal box that you found lying around somewhere and couldn't see the inside of. It's your boat, clean your tanks (don't get your drawers in a bunch over this, meant it as a light hearted call to action