Step 5 · Use a Drain Auger for Stubborn Clogs
If the water flush doesn't work or is only partially effective, the next step is to use a drain auger, also known as a plumber's snake. Insert the tip of the auger cable into the vent pipe. Carefully feed the cable down the pipe until you feel resistance, which indicates you've reached the clog. Once you hit the clog, begin to turn the auger's handle clockwise while applying steady, gentle forward pressure. You will feel the auger either break through the blockage or hook into it. If you feel it hook the clog, you can try to pull it back up and out of the vent. If it breaks through, you will feel a sudden release of tension. Feed the auger a few more feet to ensure the path is clear, then retract it.