At the start of the season I add ¼ cup of beach to 15 gallons of water and dump it in the fresh water tank. I open the facets to until I can smell the bleach. This includes the hot water heater.
Two days later, I drain the fresh water tank, refill with fresh water, and flush the facets. All this also help flush the residual antifreeze that always seems to remain in the lines. This is what the TT manual recommends.
I do drain the water tank between trips; including the hot water heater because it is really funky smelling, but I only “sanitize” the system at the start of the season. We usually stay at State Parks with only electric hook ups, so we haul 15 to 20 gallons of fresh water and refill as needed from the campground supply. We also have had no problems with campground water hook ups when they were available.
Some people are sensitive to their water supply, but the DW and I have grown up on iron rich Indiana well water or at times chlorinated and fluorinated city water, so TT water is no big issue to us. Besides, I do not flush my home hot water tank or purge my water softener tanks when I return from a several weeks trip and who know what lurks in them?