Here is a good tip I picked up a few years ago. After Chlorine sanitizing your potable (fresh) water tank and system, and after a couple of flushes, carry out the exact same procedure again but this time use Apple Cider Vinegar, not Chlorine (bleach). Why does this work? Vinegar is an Acid which neutralizes the Alkali Chlorine. After a couple of flushes, if there is any aftertaste at all it is one heck of a lot more pleasant than Chlorine! You could use standard White Vinegar to the same effect but aftertaste, (if any) would not be quite as pleasant.