Please, No Cheating Mr. Plumber

​​There is a reason they have been called "cheater vents." Air Admittance Valves (AAVs), also known as "studor vents", are devices used in plumbing systems to vent sewer gases and allow air to enter the plumbing system without the need for a traditional vent pipe through the roof. They rely on a mechanical valve that opens to allow air into the system and closes to prevent sewer gases from escaping. Accumulation of debris or damage to the valve can lead to malfunctions. Thus, AAVs require periodic cleaning and inspection to ensure proper functioning. While AAVs are easy to install, which is presumably why plumbers prefer to use them, there are other potential issues besides the maintenance required:

• Performance Issues: AAVs may not function as effectively as traditional vent pipes.  In some cases, the valve may fail to open properly, leading to drainage issues or the accumulation of sewer gases. AAVs also have limitations on the volume of air they can admit into the plumbing system. In a busy kitchen or bathroom with multiple fixtures draining simultaneously there may be insufficient airflow, leading to slow drainage or gurgling sounds.
• Installation Height: AAVs should be installed above the flood level of the fixture they serve, otherwise they can overflow (leak) during a drainage backup. Achieving the required height can be challenging due to space constraints.
• Local Odor Issues: While AAVs are designed to prevent the escape of sewer gases, there is still a potential for localized odor issues, especially if the valve malfunctions or if there are changes in pressure within the plumbing system.

If you have AAV's installed in your home (that you routinely clean and inspect, of course), you may never run into any of those issues. But, if you do run into problems, simply replacing the old AAV with a new one may temporarily resolve the issue. However, the more durable solution requiring little to no maintenance would be to install or connect to a traditional vent stack to the roof. If that is not feasible, there are other options, such as:
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• "Island", "Loop", "Circuit", or "Bow Vent": This type of venting system (that has many names) was designed for kitchen islands. It involves running a vent pipe from the island to connect with the main vent stack or vent system elsewhere in the building (at the proper height, of course). This allows for proper venting without the need for a pipe extending through the roof directly above the island. See the diagram below and click here for a video describing how a loop vent functions.

• ​​Mechanical Ventilation Systems: In some cases, especially in commercial kitchens or areas with complex plumbing configurations, mechanical ventilation systems may be used. These systems use fans or blowers to create airflow in the plumbing system.
• Wet Venting: Wet venting involves combining the venting of fixtures with the drain lines. This can be a space-saving solution, but it requires careful design and adherence to plumbing codes.
  
• Approved Alternatives: Local plumbing codes and regulations may specify approved venting methods for specific situations. Always check with local authorities to ensure compliance and to explore any alternative venting options allowed in your area.