Originally Posted by gordwedman
...If you fill your tanks from city water I don't think you need to be too concerned about microbiological contamination. You mainly want to remove paticulate matter from the tank and lines, maybe organic compounds as well. These filters should do a good job at that....
Mostly true, but not quite. The city water should be safe from a human pathenogen standpoint, but that is not the same as saying it will not breed bacteria, weird smells, and tastes.
Unless the tank is kept clean of biomass and dirt, bacteria will grow in the dirt, even in the presence of some chlorine from the city water. The residual cannot sterilize through layers, and it dissipates when the boat is unused.
These bacteria, in the absence of oxygen, will use sulfate as an oxygen source (electron donor) and produce hydrogen sulfate and other objectionable smells, depending on the base water chemistry.
Additionally, if you put glycol in the tank in the winter (common mistake--glycol should only go in the lines) it will ferment and create bad tastes that are hard to remove.
Bottom line. If you visited a restaurant you would like to know that they clean and sanitize their water tank on a regular schedule, wouldn't you? You'd like to know that bugs could not crawl in the vent. You would probably turn down a glass of water that had been setting on the counter for several months. A good NSF 53 rated in-line filter, filling pre-filtration and annual cleaning
, and you will be good.