We've been traveling for 13 years and have never been water sick to our knowledge. We clean the system with a 1/2 cup of bleach every year.
Recently I read an article where they drilled a hole a mile deep into the floor of the ocean. Surprisingly, a teaspoon of the material from a mile deep contained the order of 1000 bacteria and 10,000 viruses. For comparison, a teaspon of soil from your front yard contains billions, if not trillions, of bacteria and viruses. The reality there is no
escape. They are truly everywhere and an intimate part of our life.
Of course we should use clean water but I don't think we should lose sleep over the public or trailer water supply.