I called Roto-Rooter Plumbers in Seattle and they had a plumber, Joe Thompson, at my house in less than an hour. He rooted out my sewer line, found roots growing in it and applied a root killer within an hour.
He was pleasant and knowledgeable and hopefully won't be back soon. A little pricey, $400.00 for it all, but with a guarantee to come back for free if it plugs up again within 30 days.
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