Jain 12090023 1" MPT Air / Vacuum Relief Valve (VBK) is durable, weather resistant and non-corrosive material. One of the key elements in a drip irrigation system is air relief. Clogged emitters can create substantial voids in coverage which can lead to dead plants and dry turf. Installing automatic air relief valves on the end of lateral lines and emitterline will prolong the efficiency of your system.