Step 5 · Check and Clear the Plumbing Vent Stack
If snaking the drain doesn't solve the gurgling, the problem is almost certainly a blocked plumbing vent on your roof. The vent allows air to enter the system, preventing a vacuum from forming. Using a sturdy, well-placed ladder, access your roof safely. Locate the plumbing vent stack, which is usually a 2- to 4-inch diameter pipe (often PVC) extending from the roof. First, perform a visual inspection of the opening for obvious blockages like leaves, bird nests, or animal debris. Use a flashlight to look down into the pipe. If you see a blockage near the top, try to remove it by hand (with gloves on). For deeper clogs, you can use a garden hose with a high-pressure spray nozzle to flush the debris down. Alternatively, you can run your plumber's snake down the vent to break up the clog. Restoring airflow will stop the gurgling.