Here is the rub, you need to flush your system first then sanitize it before you even think of filling it with potable water for you to use. Use the outside faucet of your home to flush system and see if there are any leaks. You shouldn't be using any of the water you flush things out with anyway. Look up how to sanitize your system. When you go camping are you hooked up to campground water supply or do you run off of your tanks a lot of the time? I do think you are obsessing a bit much over it. Its not that complicated.