Whenever we plan a remodeling job that involves re-routing of plumbing lines, we must not only look at the hot and cold water source lines as well as the drain lines, we also need to consider venting.
We have all experienced how liquid in a drinking straw will remain in the straw if we hold our finger over the top end while raising it up out of our glass. Once we release our finger, the liquid drains out quickly, as air can easily come in to replace it. Similarly, without air able to freely enter the drain lines in our plumbing system, drainage cannot easily occur, because a vacuum is developed. AAVs are pressure-activated, one-way mechanical vents, used in plumbing systems to eliminate the need for conventional pipe venting and roof penetrations associated with vertical vent pipes. A discharge of wastewater in the plumbing system causes the AAV to open, releasing the vacuum and allowing air to enter plumbing vent pipe for proper drainage.
Whenever water isn’t being discharged into the system, the AAV remains closed, preventing the escape of sewer gas, and maintaining the trap seal. Using AAVs in a plumbing system can significantly reduce the amount of venting materials needed, increase plumbing labor efficiency, allow greater flexibility in the layout of plumbing fixtures, while reducing long-term maintenance problems associated with conventional vent stack roofing penetrations.
Standard plumbing systems use water trap seals to perform the critical function of preventing sewer gas from emanating into living areas, with fresh air pipe venting commonly used to prevent siphoning of water held in the traps. Although this method is simple and reliable, it requires each plumbing fixture to have a lateral return vent that passes through wall studs to a central stack, or to have its own vertical vent that passes through the wall, ceiling, attic, and roof. Air Admittance Valves are mechanical devices designed to maintain trap seals without the need for additional vent piping. They are one-way valves that open only under negative pressure (created when a toilet is flushed or a drain stopper is opened). When the water flow stops, the valve closes, preventing the escape of sewer gasses under conditions of equal or positive pressure.
AAVs are typically made from polyvinyl chloride (PVC) plastic materials, with rubber (EPDM) valve diaphragms. Valves come in various sizes: small ones for fixture venting and a larger sizes for system venting. The valves fit standard diameter pipes, ranging from 1-1/4 to 4 inches. Integrated screening protects the valves from foreign objects and vermin. ASSE (American Society of Sanitary Engineers) standards require that AAVs be tested to reliably open and close a minimum of 500,000 times, (which translates to at least 30 years of regular use), with no emanation of sewer gas. Some AAV manufacturers test and certify their products up to 1.5 million cycles, simulating at least 80 years of use. Air Admittance Valves have been effectively used in Europe for more than two decades, and they are now becoming more widely accepted here in the US, with an increasing number of state and local building codes allowing for their use. Domestic manufacturers of AAVs offer warranties that range from 20 years to lifetime.
Affordability – An AAV costs between $25 and $40, depending on size. The AAV device cost is typically offset by the cost of the vent pipe that it eliminates. AAVs also typically reduce requirement to coordinate labor between various trades (e.g. it eliminates the need to coordinate work schedules between roofers and plumbers, by entirely eliminating the need to touch the roof), and also reduce overall labor time for system installation because they reduce vent pipe installation, resulting in a significant net cost savings.
Design Flexibility – Because AAVs can be placed in almost any wall or cabinet where plumbing is located, they can be leveraged in many remodeling situations where the desired plumbing fixture configuration cannot be achieved with traditional vent stacks, due to lack of easy access to the roof, etc. Implementation of AAVs creates a much wider range of options for the remodeler who knows how to use them. For example, AAVs solves problems associated with venting island sinks, wet bars and other fixtures in difficult locations.
Quality and Durability – Because air admittance valves eliminate the need for vent stack penetrations and flashing at wall assemblies, attics and roof decks, they significantly reduce the potential for air and water leakage that can occur with traditional vent stack penetrations.
Increased Building Sanitation – AAVs prevent vermin and pests from entering the buildings through open vent pipes, while also reducing pollution of the environment by sewer gas, and preventing sewer gases from being drawn into air conditioning units and air handlers where they can pollute habitable spaces.
Increased Safety – AAVs eliminate the possibility of shearing off of roof vent pipes due to snow slides, while reducing the number of fire-stop devices required in construction of the building (wherever pipes penetrate ceilings, roofs, etc), and reducing the structural damage caused by holes that must be drilled through joists and studs to install traditional open-vent piping. Their usage also lowers or eliminates the risk of plumbers falling from ladders and roof tops while performing installation of open vent pipes.
Improved Aesthetics – Utilization of AAVs reduces unsightly vent pipes in the building roofline.
Air Admittance Valves substantially simplify venting of drain water venting systems in commercial and residential applications, without jeopardizing the health, safety and welfare of the public.
At A Master’s Hands, LLC we perform all types of remodeling projects for our clients, including bath, kitchen and basement remodeling. We’re very experienced in the use of AAVs, and leverage them wherever it makes good sense, resulting in savings for our clients. The inventor and most prevalent maker of AAVs is Studor, Inc., and thus, these devices are often called Studor Vents by those in the building trades.