Black tank dump plumbing replacement?

BAD BAD IDEA! It's not just common sense and I can't recite them but there are strict codes to keep sewage and gray water isolated and handled properly and to protect your health and potable water! Back flow preventers, vacuum breakers, one inch minimum air gaps between any drain and water that even comes from a potable source and on and on, just for starters. Connecting black and gray would turn the entire drain system into a black system and that would be one step closer to contaminating the potable water. Sewage in sinks and showers, so close to the potable water system, not to mention sewage smell every time there was a dry trap. Unimaginable... don't do that to yourself! Craig