We have a three story house. We have three bathrooms; two on the top floor; and one on the main floor. The kitcher and washer and dryer is on the main floor as well. I ran the dishwasher and laundry. The sink in the kitchen backed up and the toilet began to overflow when the laundry rinsed. The water in the toilet was definitely laundry water. Could this be a clog in the toilet or could our septic be backed up. We are a family of six (four preteens who do a lot of laundry). Help!