I fill up my portable water bottle (fresh water tank-----80 gallons)
I use on-board pump (RVs are self-contained) to supply rv plumbing system...cold/hot
I drink it, I wash with it, I shower with it, I flush toilet with it etc.
When the 80 gallons has been redistributed from fresh water tank to the black tank (poop), to the grey tank (Shower/bathroom sink) and to the galley tank (kitchen sink) I dump it and start all over
Good water in.......dirty waste water out....repeat over and over and over and over