AIRVAC Vacuum Sewer System

Valve Pit l Vacuum Main l Vacuum Station

The 1-piece rotationally molded PE valve pit package consists of the 3” AIRVAC vacuum valve, an upper chamber and lower chamber, the in-sump breather unit, and the air intake. The valve pit serves as the conduit through which sewage from homes enters the vacuum sewer system, flowing via gravity into the sealed sump that is part of the pit package.

Sewage level sensing is remarkably simple. As the sewage rises, air trapped inside the empty 2” (50 mm) diameter sensor pipe pushes in a diaphragm in the valve's controller/sensor unit, signaling the valve to open. When 10 gallons (38 liters) of sewage accumulates in the sump, the valve automatically opens. The differential air pressure propels the sewage at velocities of 15-18 ft/sec (4.5 to 5.5 m/s), disintegrating solids while being transported to the vacuum station. The valve stays open for four to six seconds during this cycle.

Valve pit package

The valve pit provides the interface between the vacuum system and the house. The 1-piece valve pit is rotationally molded and made entirely of PE. It consists of two (2) separate chambers; an upper chamber that houses the vacuum valve and a lower chamber that is the sump into which the building sewer is connected. These two chambers are sealed from each other. The 1-piece AIRVAC valve pit includes an integral anti-buoyancy collar and has an H-20 traffic load rating.

Each valve pit can accommodate sewage from up to four homes, although the most common configuration is one valve pit serving two adjacent houses. Houses connected to the vacuum sewers do not need any special plumbing fixtures.

Vacuum valve

Located in the upper chamber is a vacuum interface valve, which is pneumatically controlled and operated. Vacuum from the sewer line opens the valve and outside air from a breather pipe closes it. The interface valve is a full-port 3” (75 mm) valve and designed for handling 3” (75 mm) solids.

Upper chamber

The upper chamber, made of a PE material, houses the vacuum valve and controller and is suitable for H-20 traffic loading..

Lower chamber (Sump)

The sump portion of the valve pit is used to accept the wastes from the house. Elastomer connections are used for the entry of the building sewer. Holes for the building sewers are field cut by the contractor at the position directed by the engineer.

In-Sump breather unit

The AIRVAC controller requires a source of atmospheric air to the actuator chamber permitting spring assisted closing of the vacuum valve. Without this air, the valve will remain in the open position.

Early vacuum systems used an external breather for this source of air. This has been replaced by the in-sump breather, which uses atmospheric air from the sump. In the event of low vacuum conditions where the valve would not open, floats in the in-sump breather protect the controller from unwanted liquid.


Atmospheric air used for transport enters through the 4” (100 mm) screened air-intake on the homeowner’s gravity line. The possibility of odors at this air-inlet is minimized due to the small volumes of sewage and short detention time in the sump.