Routine mainline cleaning is conducted with a high pressure "jetter" truck to effectively scour the interior of the pipes, effectively removing debris from the wastewater system. The City crew utilizes a Hi-Vac truck equipped with a ¾ -inch 1000-foot long hose that creates up to 3000 pounds per square inch (psi) of water pressure. Wastewater staff access the sewer system from manholes in the street. They work quickly to minimize the inconvenience to customers and maintain a safe work environment.
Wastewater Technician operating the high pressure “jetter” truck to remove debris from the mainline via a manhole in a City street.
Tree roots are the most common natural obstruction found in sewers. The Wastewater Maintenance Crew mechanically cuts and chemically treats tree roots that could potentially obstruct the wastewater main. Trouble areas are monitored yearly for root intrusion.
The City's entire 218 miles of pipe are cleaned at least every 3 years with some areas cleaned yearly. This proactive maintenance approach has led to an average of only 3 sanitary sewer overflows per year as compared to the national average of 4.5 overflows per 100 miles of wastewater pipe. (That’s nearly 10 sanitary sewer overflows for a service area our size!)
Here's a video of routine mainline cleaning produced with Redmond's closed circuit television (CCTV) system. The video shows the end of the high pressure "jetter" hose scouring the interior of a wastewater pipe. The bottom of the pipe has been visibly corroded by wastewater flow. The video ends once the robotic camera system reaches a manhole.