Frequently Asked Questions – Studor

Air Admittance Valves (AAV)

Q. How does the Studor Air Admittance Valve work?
A. The Studor Air Admittance Valve (AAV) is a one-way valve that allows air to enter the plumbing drainage system when fixtures discharge. The valve closes by gravity when discharge is completed and under no flow conditions preventing sewer gas from escaping into the valve.

Q. Why is it important to allow air to enter the plumbing system?
A. When fixtures discharge negative pressure develops in the drainage system due to water flowing downstream in the pipes. If air does not enter the system and balance the pressure the water in the fixture trap will be siphoned allowing sewer gas to enter the building.

Q. Are Studor AAV’s suitable for all applications?
A. YES! Studor manufactures various models which fit pipe sizes of 1 1/2″, 2″, 3″ and 4″. The valves are suitable for single fixtures, branches and stack applications in residential and commercial buildings.

Q. Can Studor AAV’s be used in extreme temperatures?
A. All Studor AAV’s are tested to temperatures of -40° F and +150° F as required by the ASSE Performance Standards. In addition some models are provided with insulation material as part of the packaging which provides additional protection.

Q. Can Studor AAV’s be used outdoors?
Studor AAV’s can be used outdoors, but it is recommended that they be protected from the elements.  Download more information.

Back to top


Q. What is a Chem-Vent?
A. The Chem-Vent is a specialty Air Admittance Valve (AAV) manufactured by Studor.

Q. What is its intended purpose?
A. The Chem-Vent was purposely designed to be used in specialized acid waste systems as a replacement of conventional vent pipes and loop vents (very commonly used in lab style layouts).

Q. What kind of acid waste systems?
A. The kind commonly installed in schools, hospitals and labs in general.

Q. Can the valve be used in systems handling bio-hazardous or otherwise toxic waste?
A. The valve CANNOT be used in any applications where the fumes contained in the waste systems would require filtration before humans could be exposed to them.

Q. Can any material AAV be used in acid waste systems?
A. No, technically, only the Chem-Vent since all its components are designed to handle the corrosive and temperature environment of an acid waste system. Standard (residential or other commercial) AAV have neither the chemical resistance nor the temperature range to operate in such systems.

Q. Is the use of the Chem-Vent in acid waste systems code approved?
A. Currently the plumbing codes do not allow the use of any AAV’s in an acid waste system. This application was correctly excluded in the codes because no manufacturer produced a suitable product. Studor’s Chem-Vent is different and Studor is working with the code authorities to make an exception for AAV’s manufactured from chemical- and acid-resistant material.

Q. Can the Chem-Vent be used before the code language is changed?
A. Even before the code is changed it will be possible to use the Chem-Vent as part of an engineered system.

Q. What makes the Chem-Vent different from all other AAV’s?
A. Its Flame Retardant Polypropylene (FR-PP) material of construction and its chemical resistance EPDM seat.

Q. Why FR-PP?
A. For the last 20 years FR-PP has been the material of choice in the vast majority of institutional lab installations (e.g. schools, hospitals, etc.)

Q. Are there any other material used in acid waste systems?
A. Yes, starting from the oldest to the newest:

  • Ductile Iron (Duriron®)
  • Borosilicate glass
  • CPVC

Q. When, where and why are these materials used instead of FR-PP in Acid Waste piping systems?
A. Duriron was the very first system used in acid waste system before better materials came along. Its chemical resistance is very poor and so is its life expectancy. The Chem-Vent can be comfortably specified and used on any Duriron systems.

  • Glass replaced Duriron as the material of choice and is still extensively used today in return air plenum applications as well as with some extreme chemicals. Cost, limited jointing styles, brittleness and difficulty of installation of glass have allowed FR-PP to become the predominant choice. If FR-PP is deemed resistant to the chemical waste in a glass system, the Chem-Vent can be used on glass systems unless the system is installed in a return air plenum.
  • FR-PVDF is a relatively new material designed specifically to replace glass in return air plenum installations. Although comparable in material cost its versatility, light weight and available jointing systems makes the installed cost of FR-PVDF systems in return air plenum very competitive with glass. If FR-PP is deemed resistant to the chemical waste in a glass system, the Chem-Vent can be used on glass systems unless the system is installed in a return air plenum.
  • CPVC is the newest material in acid waste system. Like FR-PP it cannot be used in return air plenum applications; additionally it cannot be used if solvents are part of the waste flow. Thanks to its proven solvent cement jointing system CPVC is easy to install and does not require specialty equipment. The Chem-Vent can be comfortably specified and used on any CPVC systems.

Q. How does the Chem-vent connect to an FR-PP system?
A. The valve’s extended tail piece can be directly installed on any mechanical joint or fusion sanitary Tee currently available (regardless of the manufacturer) following the acid waste system manufacturer jointing instructions.

Q. How can the Chem-Vent be installed on dissimilar material systems?
A. Through adapters designed to transition from FR-PP to glass, ductile iron or CPVC.

Q. Where can I find these adapters?
A. FR-PP to glass or ductile iron adapters are readily available through the different FR-PP piping system manufacturers. FR-PP to CPVC adapters are readily available through the different CPVC piping system manufacturers.

Q. Why does the Chem-Vent have an extended tail piece connection?
A. To make sure that the vent will always comply with the code required minimum of 4″ above the trap, no matter which FR-PP manufacturer or system is selected.

Q. Does the Chem-Vent meet any performance standards?
A. Yes the Chem-Vent is tested to and certified to; NSF 14

Back to top


Q. What is a Maxi-Filtra?
A. The Maxi-Filtra is a device that serves as a two way vent that allows air to pass through a carbon filter and eliminate sewer gas odors.

Q. Can the Maxi-Filtra be use indoors?
A. No, the Maxi-Filtra is designed for outdoor use only, particularly for use with septic systems.

Q. Can the Maxi-Filtra be installed horizontally?
A. Yes, the Maxi-Filtra can be installed in the horizontal or the vertical position.

Q. Can the Maxi-Filtra be installed in an existing system?
A. Yes, the Maxi-Filtra can be retro-fitted on an existing system.

Q. How long does the carbon filter cartridge last?
A. The cartridge can last up to 2 years.

Q. Does the Maxi-Filtra require maintenance?
A. No maintenance is required other than replacing the cartridge.

Q. Is the Maxi-Filtra protected from UV rays?
A. Yes, there is also an optional cover available for additional protection.

Q. What size pipe does the Maxi-Filtra fit?
A. The Maxi-Filtra fits a 3″ or 4″ pipe.

Back to top


Q. What does P.A.P.A. stand for?
A. Positive Air Pressure Attenuator

Q. What is the P.A.P.A. used for?
A. It is used to neutralize positive air transients in the DWV system of multi-story buildings.

Q. What is a Positive Air Transient?
A. It is a low amplitude, high speed air pressure wave traveling through the system.

Q. How fast does it travel?
A. 1056 ft/sec – the speed of sound.

Q. Does it represent a large volume of air?
A. No, typically it is no more than 1/2 gallon of air. It can, however, be greater depending on conditions.

Q. Why are Positive Air Transients created into a DWV system?
A. Fluids discharged into a DWV system, after reaching terminal velocity, begin to swirl inside the pipe, dragging air into the center of the pipe. After the pipe transitions from vertical to horizontal (bottom of the stack or change of directions) a curtain of water is formed. The air hitting this curtain bounces off of it and travels backward through the system.

Q. Are Positive Air Transients the only potential for positive air pressure in a DWV system?
A. No, positive pressure can also travel into a buildings DWV system from sewer (or septic tank) or be generated by a blockage(or belly in the pipe).

Q. Is the P.A.P.A. designed to neutralize all positive air pressure conditions?
A. No, just Positive Air Transients.

Q. Why are Positive Air Transients harmful to a DWV system?
A. They can result in the loss of water seals or, at a minimum, contribute to the depletion of the traps. Positive air transients ave been proven to resonate inside of conventionally designed systems up to three days. In addition they can be the source of bubble through; a condition that allows sewer gases as well as pathogens to be introduced in to the living space without loss to the trap seal.

Q. How are Positive Air Transients typically dealt with?
A. Relief Vent
Sovent System – This system deals indirectly with the positive air transient slowing down the flow in the system thus preventing terminal velocity to be reached. Special aerator and de-aerator fittings must be used at each branch in order to prevent the formation of positive transients.
Single Stack system – (Philadelphia system) – The Single Stack system relies on venting through the roof, with consequent increased roof penetrations.

Q. Is a P.A.P.A. / AAV system better than these other systems and if yes, why?
A. Technically it is better for four reasons:

  • System balancing in 0.2 seconds
  • Neutralize almost 100% of the transient
  • Eliminates floor and roof penetrations
  • Maintains the natural flow in the system
  • In addition, it also represents substantial savings over the other designs.

Q. Why would most of the transient naturally flow in into the P.A.P.A. if it is attached to a smaller branch, much like a relief vent?
A. Because the instant a minimal portion of the transient begins to inflate the P.A.P.A. bag a differential pressure is created at the branch-off point making the branch and the P.A.P.A. the path of least resistance for the air.

Q. What happens to the air transient once it enters the P.A.P.A.?
A. Its velocity (1056 ft/sec) is instantly (less than 0.2 sec) cut to 40 ft/sec after which the small (and now slow) air volume is harmlessly re-introduced into the system.

Q. What if it is determined that there is the potential for a greater than average air volume?
A. Up to four P.A.P.A.’s can be serial mounted for up to a total volume capacity of 4 gallons.

Q. Is the P.A.P.A. a maintenance item?
A. No, it does not require maintenance since there are no stress pieces, springs or mechanical devices that could wear or lose tension and consequently fail.

Q. What kind of warranty does it carry?
A. The P.A.P.A. has a limited lifetime warranty for replacement of defective product.

Q. Must the P.A.P.A. be installed vertically?
A. No, it can be mounted in any position and orientation (unless used with an AAV on top)

Q. Where should the P.A.P.A. be installed?
A. It should be installed at the bottom of each stack in the building below the first branch and before the sweep transitioning the pipe from vertical to horizontal. Additional units may be required on each stack, depending on the number of branches (see our installation guide)

Q. Can the P.A.P.A. be retrofitted to an open pipe vent system?
A. Yes

Q. Can it be engineered as an integral part of an open pipe vent system as additional protection?
A. Yes

Q. What can the P.A.P.A. be compared to in order to give customers a quick understanding of its function?
A. In essence, the P.A.P.A. performs a function similar to that of a water hammer arrestor, but for air.

Back to top