Step 2 · Locate the Plumbing Vent Stack
Once you are safely on the roof, you need to locate the plumbing vent stack. Look for a vertical pipe, typically 1.5 to 4 inches in diameter, extending through the roof. It's usually made of white PVC, black ABS plastic, or sometimes older cast iron. These vents are typically positioned above the home's bathrooms or kitchen, as they connect to the main drain lines. There may be more than one vent stack on your roof.