Old GE dishwasher... OK when washer machine runs it backs up to kitchen sink and fills dishwasher.. all 3 aligned in straight line, I ran a snake on roof vent, it's a one story home so I ran 40 feet of 5/8" snake and pulled up what looked like heavy black ooze (mud?)... there is no vent outlet on sink for dishwasher, no garbage disposal, it has a small line connected to water line under sink... I do not know how to check drain pump on this dishwasher so I am not sure what to do next... also outside of home on the opposite end is a clean out drain, has a big square plug and I have not tried that yet... if I can access that clean out and run that same snake through it, I assume I need 75-100 feet of line does that one cleanout take care of it?