Step 2 · Locate the Main Cleanout

Locate the main line cleanout in your basement. It is typically a large-diameter pipe (3 or 4 inches) made of cast iron or PVC that runs horizontally near the floor and exits through the foundation wall. You are looking for a 'Y' shaped fitting with a threaded plug or cap at the top of the 'Y' branch. The plug often has a square, raised nut on its top for a wrench. Use a flashlight if the area is poorly lit to confirm you have identified the correct access point.