The drain line from my kitchen sink drops down through the basement, into the basement floor (Concrete), and I assume under the floor to the main sewer line. The sink tends to drain slowly. Should I have a separate vent at the sink, or is it OK if the only vent is the main vent stack?
Should I snake out the line to see if it helps, or is this more likely a problem with not having air behind water?
I have already taken apart and checked all the pipe that is above the basement floor (and it was clear), if there is a clog it would be in the line that runs under the basement floor.