Air Admittance Vent Views
Air admittance valves (AAVs or Durgo valves) are negative pressure-activated, one-way mechanical vents, used in a plumbing system to eliminate the need for conventional pipe venting and roof penetrations. A discharge of wastewater causes the AAV to open, releasing the vacuum and allowing air to enter plumbing vent pipe for proper drainage. Since AAVs will only function under negative pressure situations they are unsuitable for all venting applications, such as venting a sump, where positive pressures are created when the sump fills. Using AAVs can significantly reduce the amount of venting materials needed in a plumbing system, increase plumbing labor efficiency, allow greater flexibility in the layout of plumbing fixtures, and reduce long-term roof maintenance problems associated with conventional vent stack roofing penetrations.
While some state and local building departments prohibit AAVs, the International Residential and International Plumbing Codes allow it to be used in place of a vent-through-the-roof. AAV's are certified to reliably open and close a minimum of 500,000 times, (approximately 30 years of use) with no emanation of sewer gas; and some manufacturers claim their units are tested for up to 1.5 million cycles, or at least 80 years of use. Air Admittance Valves have been effectively used in Europe for more than two decades. U.S. manufacturers offer warranties that range from 20 years to lifetime.
The purpose of venting plumbing is to allow air to enter the plumbing drainage waste and vent piping system and equalize pressure when water drains out of the system maintaining the integrity of the water trap seals that prevents sewer gases from entering the building through fixture drains. Air Admittance Valves open and close in conjunction with normal (DWV) Drain Waste and Vent, plumbing system operation. When a plumbing fixture is operated a negative pressure (induced by fixture discharge) causes the AAV to open and allow air to enter the DWV system. The air equalizes the pressure within the system, protecting traps and eliminating the chance of siphonage - at no time is drainage flow disturbed. The time it takes for an AAV to open is extremely short, assuring that it responds to system needs. Static or positive pressure closes the AAV, eliminating sewer gas from entering the building.
An Air admittance Valve (AAV) allows air to enter the plumbing drainage system through a one-way air valve when a plumbing fixture is operated and water flows through the pipes. When the flow stops, the valve closes by gravity and prevents the escape of sewer gas from the plumbing system. AAVs allow greater freedom of design for plumbers, engineers and architects.
Air Admittance Vent Images
