[GaryWT]

I generally do not use the tank as we usually have hook ups, actually filled the tank last week just to flush it out as well as the pump. I would think a week or so and if unused you would change it. No different that the coffee pot at home, if it is not used for a week or so we usually domp the water and refill. Other than weight, this is probably another reason people wait until they get to where they are going to fill if available. We too drink bottled water while camping. We have small bottles for drinking and gallons for coffee and cooking.