I had one of those. I tended not to use it after the red, blue and black ink was gone. Why bother with green ink?
Ok that story .. oh man please someone Denny this as sarcasm ..Is that since the alleged incident at the Olive Garden in Warren, Michigan.
Just flush it once or twice and the water should be the same water you get out of the tap (unless you have extra filtration or something for your taps). I'd be more worried breathing the air on the other side of that water.
The sewer lines should be vented. This is a life or death maneuver…Foo gas is poisonous.