Leaving water in fresh water tank

I keep my 80 gallon tank full at all times. I travel with afull tank at all times Generally it sits no longer than a month at max. 2 months. Never an odor never a problem.
I fill from a chlorinated source. I avoid filling from an unknown source. If I have to fill from an unknown source, I will drain and refill from my known trusted source when I return home.
A full tank contains less air and less chance for bacteria growth. An empty tank is a dark damp place which is ripe for bacteria growth.
Even when dumped/emptied the tank is not totally bone dry. There is always a considerable amount of residual water left. I believe I am better off totally full vs. totally empty.
Having a full tank also give me peace of mind. I have a on board genset. My RV is fully self contained at all times which is nice case of power outages, foul weather or any natural disaster.

I never tow with much water in my trailer. Adds considerable weight. If dry camping I fill the tank close to my destination. When heading home I empty most of it although there is usually none left.

Most of the time we have full hookups. Either way we generally do not drink or cook with tap water. Use it for showers and dishes.

Fill a drinking glass with the water that is in your tank and then drain the tanks completely. Store the glass of water in a dark place and let it stand for the period of time you would store the trailer. At the end of that time evaluate the water you stored and that will answer your question. If the water is cloudy/smells or has any sign of bacteria and you had previously drained the tank you have no problem either way. If you did not drain the tank you need to clean the tank with Clorox.

When we used to have our motor yacht we had an issue with leaving fresh water in the tanks for long periods of time. Sometimes we would have 70 or 80 gallons of fresh water on board for a couple of weeks before returning to the boat and living on it.

We used a additive called Fresh Water. We generally purchased it from Walmart and it was pretty cheap. It worked extremely well for preserving the fresh water. Not sure what the chemical make-up of it was.

Chlorine is a gas, unless pressurized, like propane. Unless your tank is hermetically sealed, chlorine will dissipate, and fairly rapidly at summer temperatures.

btw, Bromine is often used for hot tubs because it dissipates at a slower rate than chlorine at higher temperatures. Just fyi, not terribly relevant here.

I often leave water in my fresh water tank all summer. But I seldom if ever would drink it, and I run water for ice-making through a filter at the faucet. Actually, 9 times out of 10, I use full hookups, which is why water could be in the holding tank all summer.

Thanks for all the replies...

As for adding chlorine/bleach I don't know that the pool example is a good one. Chlorine is extremely susceptible to the Ultraviolet (UV) rays from the sun, which can use up your chlorine rapidly in a pool but in an RV holding tank this obviously is not an issue.

Up here ours would freeze, so it has to be drained.

Chlorine/chloramine will loose it's effectiveness over time (it's why people need to periodically add chlorine to hot tub/pools) .. so if it sits for a long time you might consider adding a bit of bleach. My water rates are probably higher than yours and I drain mine so it goes into a plant bed.

Maybe you'll get a plastic taste but nothing harmful.

I will only drain mine if I think it came from a questionable source and that it may not be properly purified.