Soil 110mm Air Admittance Valve Black (Male, No Rubber)This 110mm black air admittance valve from Davant is also known as a durgo valve and works by allowing the entry of clean air into the sanitary waste water system without the escape of foul gasses into the property. Whenever negative pressure is created it can siphon water traps and allow unpleasant smells to enter the property. This air admittance valve quickly acts when negative pressure is created by opening and letting clean air enter which