Prevent damage to the drip irrigation system due to water hammer and cavitation with the 1/2 in. MPT Air/Vacuum Release Valve. This device, also known as an air relief valve, releases trapped air in the pipeline to clear blockages and allow water to flow through. When water evacuates, the valve also fills the void with air to prevent vacuum suctioning of debris into the line that can clog and damage emitters. The valve has a 1/2 in. MPT connection point and is made of durable plastic.