When the pipeline is filled and pressurized, the large air/vacuum orifice stays closed. The smaller diameter air release orifice remains open to allow small pockets of accumulated air to escape automatically and independently of the large orifice.

When filling or draining the pipeline, the large air/vacuum orifice shuts opens to allow large volumes of air to escape or enter. When the free floating-center guided plug is raised into the orifice by the lifting force of the concave-bottom float, the large orifice shuts off without spilling or spurting.

The ASC Sewage Air Valve provides both high efficiency and reliability in a single elongated body. The elongated body prevents sewage or dirty wastewater from fouling the venting mechanism.