I have a dilemma. My mother in law had a new bathroom put in her house. Her contractor ran her toilet/shower/sink/washer to the drain in the basement. This was done about 2 years ago. Now water is dripping from her air conditioning unit and into her furnace. (The condensation drain from her a/c is also run into the basement drain.) A furnace guy came today and upon opening the a/c unit, found it full of feces and toilet paper. She had 2 other professionals come over to look and they all say what her contractor did is illegal. He claims the basement drain goes to the sewer and it is not his problem as it has been 2 years since he did the work. My question is, does the basement drain go to the sewer as he says, or is it simply run into a drain field?