Sterilizing water system

Hi all! My first post. I hope I can explain myself clearly. We have a travel trailer. As usual it can hook up to a water tap with the white hose or use its onboard fresh water tank with its water pump. Last year I sterlized the fresh water tank and system for the first time. It bothered me to use 30 gallons of water with bleach to sterilize and then another 30 gallons to rinse and watch all that water drain down the street. This summer/fall my wife and I will likely only get to use the trailer for about 10 days of camping. Too many other commitments unfortunately. Which makes me feel worse about using all of that water. If we mostly camp with a hook up and use the white hose I'm guessing there is no reason to sterilize the fresh water tank. Does that makes sense? Should I still consider sterilizing the pipes within the trailer? If so, how?
Thanks for any input and have a great day!!