Most of it is a simple marketing ploy...and it works with many..why add chemicals to your fresh water tank to later assume it is not detrimental to one's health. You don't need it. Just make sure you are using good potable water through a proper hose. If you sanitize your tank before start of season, (search the forum here, there are tons of posts on how to do it, no need to re-hash again in this post), and if you don't let water sit in your holding tanks for weeks on end when not in use, you will be fine. Get an outside filter to filter any water before it goes in, empty your tank between trips, and always start out with fresh water and you will be fine.
2011 GMC Sierra 2500HD
2014 Rockwood 8289WS, Diamond Pkg.