This paper is about the characteristics of Air Admittance Valve(AAV) used in drainage systems, including of the types which are commonly sold in the market, such as ones used on the top of airflow pipe and used under flood level rim. Up to now, there is no research analysed the AAV characteristics and there is no concrete rules about construction program. This paper provided the characteristic analysis of AAV, load and air distributing characteristics with the drainage system worked.
