Air admittance valves replace expensive and complex plumbing vent systems that penetrate the roofs of most homes, offices, factories and warehouses. The vent pipes allow air to enter the plumbing systems and equalize pressure when water drains out of the system, maintaining the water seal that prevents sewer gases from entering the building. Air admittance valves are usually suitable for installation on PVC or ABS pipes and can be used as an individual branch, circuit or stack vent.
