In this activity, The Protagonist must devalue property throughout Stilwater by using a Stilwater Municipal Septic Truck's roof mounted Septic Spray cannon to spray waste all over buildings and people. As with Mayhem, money is earned for destroying property, and a set value goal must be reached in each level.
The Protagonist does not drive the truck, but pressing the Brake pauses the truck along the route to allow more time to spray the nearby properties.
In the Suburbs Expansion District, Javier, an estate agent, wants to bring down property values quickly before attending a party at Stefan's. The driver's name is Tony who works as a sarcastic government garbageman and is a relative of Javier.
The Septic Avenger activity is referenced in Saints Row: The Third by TV announcer Bobby when he tells his follow announcer Zach about his trip to Stilwater. He was driving in a rented convertible when it was hit by septic waste from a passing septic truck.