Fernco Air Admittance Valve

Useful Information

What is an Air Admittance Valve Used For?

The Fernco Air Admittance Valve (AAV) is an essential component in maintaining a healthy and efficient sanitary system. It is designed to allow air to enter the sanitary pipework system while preventing the escape of foul gases into the building. This innovative system ensures a balance in air pressure within the pipes, which is crucial for the proper function of the waste and soil pipe systems.

Key Features

  • Universal Compatibility: The AAV32-63 model provides a universal connector for 32mm, 40mm, 50mm, and 63mm waste pipes, while the AAV70-110 model caters to 70mm, 75mm, 90mm, and 110mm soil pipe systems.
  • Odour Prevention: Effectively prevents the escape of foul gases into the building, maintaining a pleasant indoor environment.
  • Water Trap Protection: Guards against the loss of water from trap seals, which can be caused by induced siphonage.
  • Eco-Friendly Design: Emits no foul gases, aligning with environmental conservation efforts.
  • Aesthetic Appeal: Manufactured from high-gloss white plastic, it offers a modern and clean appearance.
  • Cost-Effective: Eliminates the need for penetrating the outer roof shell, saving on the cost of additional pipes and fittings.


  • Suitable Pipe Diameters: 32-110mm for waste and soil pipes.
  • Material: High-quality, high-gloss white plastic.
  • Testing: Each unit is individually tested and numbered for assured quality and performance.
  • Standards: PN-EN 12380:2005

How does an Air Admittance Valve (AAV) work?

An air admittance valve is a device that helps to regulate the pressure within a building's waste-water (or sanitary) plumbing system. Here's a step-by-step breakdown of its function:

  1. Maintaining Pressure Balance: When water flows through a building's pipes, it creates a pressure difference. This can lead to negative pressure or a vacuum in the pipe system. AAVs are designed to respond to these pressure differences.
  2. Opening Under Negative Pressure: When negative pressure occurs (like when a toilet is flushed or a sink is drained), the valve opens, allowing air to enter the plumbing system. This inflow of air helps to balance the pressure inside the pipes, preventing the water in the traps from being sucked out. Traps are the U-shaped bends in the plumbing which hold water to block sewer gases from entering the building.
  3. Sealing to Block Gases: When there is no negative pressure, the valve remains closed. This is crucial for preventing sewer gases from escaping into the building through the plumbing system. The valve's seal is designed to be both airtight and secure, ensuring that only air can enter when needed, and no unwanted gases escape.
  4. Passive Operation: An AAV operates passively. It automatically opens in response to the internal pressure changes in the plumbing system and closes when the pressures equalize. This operation eliminates the need for an external vent pipe extending through the roof, which is common in traditional plumbing vent systems.
  5. Preventing Siphonage: By allowing air into the system, AAVs prevent the siphonage effect that can occur in sealed plumbing systems. Siphonage can draw water out of traps, breaking the seal that prevents sewer gases from entering the building.

Where does an Air Admittance Valve (AAV) need to be installed?

It should be installed into sanitary pipework systems at a point where it can effectively balance air pressure within the pipes. The valve needs to be accessible for maintenance and should not be located in areas where it might be blocked or hindered by debris or construction materials.


Fernco Air Admittance Valves Datasheet

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Grouped product items
CodeProduct NameList PriceYou SaveYou Pay Quantity
484310Fernco Push Fit Air Admittance Valve 32-63mm £22.64 30%
484309Fernco Push Fit Air Admittance Valve 70-110mm £40.51 30%