Internal/External Air Admittance Valve for 110mm Soil Pipe
McAlpine recommend that Air Admittance Valves be installed internally within the building.
AAVs should be located preferably in a non-habitable space such as a duct or roof space with adequate ventilation and must be accessible for maintenance. AAVs must be installed in the vertical position.
- Enables ventilating pipes to be terminated inside the building thereby avoiding roof penetration
- Allows greater flexibility in design of new drainage systems
- Allows greater flexibility when installing additional appliances to existing drainage systems
- Eliminates problems of freezing associated with external pipes
- Suitable for use with either plastic or metal pipes
- Offers cost savings in both material and labour
Although there are no regulations for an AAV to be installed externally, it may be advantageous in certain circumstances, be it design or otherwise, to allow installation into an external soil stack and some of the advantages are as follows:
- The external soil stack may be terminated below the roofline which reduces the amount of soil pipe and fittings required
- The AAV may be installed at a minimum height of 200mm above the highest wet branch connection
- Fitted externally the AAV is easy to access for maintenance if required
- Reduces installation time and materials
- It may be prudent to seek guidance from the local building department
The two diagrams illustrate how Ventapipe functions. The valve diaphragm lifts and allows air to be drawn into the system when it is subjected to negative pressure. On cessation of negative pressure the diaphragm returns to the closed position thereby preventing the escape of foul air into the building. The valve is designed to open and close spontaneously when required thereby allowing a supply of air to adequately ventilate the system thus ensuring a smooth discharge.