1/2″ Air Vacuum Relief Valve with BSP Male pipe thread delivers optimum performance and increased efficiency of a drip system by preventing back suctioning into the drip line. The relief valve allows air to escape the drip line during the system’s initial start and until the pipe or drip line is full of water. It also allows air to enter back into the drip line when the drip zone is turned off. Install the valve at the highest point of a drip line installation for optimum efficiency. A single Air Release Valve eliminates air pockets within a system zone.