Step 5 · Snake the Drain Line
If the P-trap was clean or cleaning it didn't solve the problem, the clog is further down the line. With the P-trap still removed, insert the end of a manual drain snake (or auger) into the drain pipe that goes into the wall (the stub-out). Push the snake in until you feel resistance. This is likely the clog. Tighten the setscrew on the snake's handle and turn the handle clockwise while simultaneously pushing forward and pulling back slightly. This motion will either break up the clog or hook onto it so you can pull it out. Retract the snake, clean the end, and repeat if necessary. You may need to feed out several feet of cable.