A few weeks ago our kitchen sink started backing up with water whenever we use the washing machine. We are on a septic system and have never had any problems until now. The house was built back in the 50's so we're not sure if there is a grease trap to be the cause of the issue. We've put root killer in the crock, but that didn't help and we just used an electric auger to try to clean out the pipes. Nothing has worked and we are very frustrated that it might be a larger tank issue. Any suggestions would be great.