Step 7 · Test the Drain Line
Before replacing the cleanout plug, you must verify the clog is gone. Ask a helper to flush a toilet on the ground floor (not the basement) a few times. Alternatively, you can run a large sink or bathtub faucet for several minutes. Watch the water flow inside the open cleanout pipe. The water should flow swiftly down the drain without any signs of backing up. If it backs up, you may need to repeat the augering process.