We had a real challenge with a "plugged" main drain line in our home. It took a while, but the service technician found that a squirrel had crawled down the sewer vent line, got trapped in the main horizontal line, and drowned. This does not happen everyday, so I give a lot of kudos to our serviceman for staying with the task at hand until he found the problem and fixed it. everything now working great again. Thank You!!