I have had many clogs in my kitchen sink over the years. I am no plumber but this is the first one I can’t fix. I have double sinks with no garbage disposals. Water will not drain in either sink. I have tried plunging the daylights out of them, liquid plumber, baking soda and vinegar, a gallon of boiling water (9x), snaked then out to about 7 feet, and have checked the U-pipe under both sinks (which are clean as a whistle). I am at a loss. Why won’t the water go down?