[Lack of HP]

Well this could be one of those dumb questions but unless you know the answer I guess no questions is dumb. I have a 14 3625re Montana, never had the fill system before using the switch on the city water hookup. Mine were always stand alone.
My question is are there any way to add a water freshener or chemical to clean the tank. Could not find anything on this.

I go to alot of Nascar and NHRA events and use Johnny on the spot to refill the fresh water tanks for showers and such. How would they do this as they don't hook up, just pump in. Thats my dumb question. I am sure I am not the only on going to these events. thanks. Joe