The two main reasons for an air release valve are: 1. A means of releasing air from the drip line when the system is turned on. Eliminating any air pockets. 2. To allow air to freely enter the system when it is shut down. This ensures a vacuum does not draw debris into the drip line via the dripper outlets. This condition is known as "suck back". Suck back can cause the drip line to collapse or potentially draw in dirt and block the dripper. Installation: To install an air release valve, ensure you have a 19mm x 1/2" BSP female iron tee at the start of your system. The air release valve screws into the 1/2" BSP female thread of the tee piece. This valve connection is normally located after the pressure reducer assembly as this is often the highest point in the drip system. It is important to install the valve at the "highest point" in the system to allow it to work correctly. If your tap & filter is lower than the irrigated landscape, ensure your air release valve is suitably located at the highest point. Install one air release valve for every 40Lpm of water flow used in your system. NOT SUITABLE for low pressure applications. The valve needs minimum operating pressure of 7 meters (70kPa to operate).