In Connecticut, Rick searches for a mysterious clog in a treatment plant's outflow pipe. In New York, George and Ramone struggle to clear a clogged reservoir.

In Mount Vernon, an abandoned sewer line is overwhelmed by stagnant human waste. And in New London, a large clog could take down a city building.

Don dives into a toxic sewer line. Ramone and George try to fix a sewage-filled basement, and Josh tries to break down a rock-solid formation of grit and fat.

Don tries to remove a massive 'fatberg' of wipes, toiletries and trash blocking a residential sewer line. Plus, Ramon discovers a huge sewer break.

In Mount Vernon, a mysterious clog backs up a downtown neighbourhood's sewer line. In Cleveland, the debris from a severe storm backs up a critical grit chamber.

In Brooklyn, Dirty Water Don repairs outflow gates at a treatment plant. In Massachusetts, Rick tackles a grease trap at a meat cutting facility.