Camper_Jeff_&_Kelli wrote:
Does anybody really know how much "Stuff" actually grows in an RV fresh water tank? Typically, it's full of or has water in it and is somewhat sealed from the outside. It's always dark in it's compartment which to algae means no light to produce food and grow. There are trace amounts of nutrients for stuff to grow from. The RV fresh water tank is really an inhospitable place for life.
Don't count on it being inhospitable. I have done a lot of trace metals lab research requiring ultrapure water. It is quite amazing how fast even ultrapure water can become contaminated and show bacterial growth. Pseudomonas is one of the most common. When the overgrowth is advanced you can feel a slime on the sides of the container and eventually you can see a pink discoloration. Fortunately pseudomonas is generally relatively harmless.
E coli contamination is also ubiquitous. One of my concerns is Legionella. Fortunately many people tolerate exposure quite well but not always. I had a friend who became very ill with it an was hospitalized for several weeks. Legionella loves heat and does quite well in RV hot water tanks:
https://www.hindawi.com/journals/criid/2013/286347/
Here is an additional study showing prevalence of bacterial growth:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5896965/
