Sanitary Sewer System
The sanitary sewer system is that part of the utility infrastructure that carries wastewater from individual properties and delivers it to the Hampton Roads Sanitation District (HRSD) for treatment at one of two HRSD sewer treatment plants in the city.
Vacuum Sewer Systems
Vacuum sewer works on the principle of differential pressure, in that the wastewater is picked up and moved through the pipe by the movement of air. Each house connection will have a valve pit and after a predetermined amount of wastewater collects in the sump, the interface valve will open and the difference in pressure between atmosphere and vacuum will draw the liquid from the sump, through the valve, into the vacuum main, and to the pump station collection tank. From the collection tank the sewer is then lifted by sewer pumps into a force main and on to one of two HRSD sewer treatment plants in the city.
Gravity Sewer Mains
Gravity sewer lines are pipes that carry wastewater to sewer pumping stations. These lines are not pressurized and are placed in the ground at specific slopes to allow gravity to carry the wastewater "downhill" to a sewer pumping station.
Sewer Force Mains
Sewer force mains are pipes that are pressurized by sewer pumping stations and carry the wastewater to a sewer treatment plant.
Sewer Pumping Stations
The city operates and maintains over 400 sewer pumping stations. A pumping station collects the wastewater collected by the gravity system and pumps it into a sanitary sewer force main for delivery to HRSD for treatment.