The 1/2" MPT air relief valve is used to allow air to escape during the system start up and also to allow air back into the drip line when the water is turned off. The air relief valve helps prevent clogging in sub-surface drip irrigation systems due to suction of debris under vacuum conditions. The air relief valve should be installed at the highest point of a drip line layout.
The air relief valve installed with a drip line or drip tape for sub-surface installations allows air into the drip line or zone when the system it is not operating. It is not required for above the surface installations. The air relief valves can reduce the chance of water hammer damage caused by a sudden reversal of water flow. The air relief valve allows air to escape during system start-up and prevents air restrictions within the system.
In any irrigation system trapped air bubbles can damage pumps (via cavitation) and disrupt the flow rate and pressure in the system. The two main reasons we suggest installing an air relief valve in an irrigation system are:
1.They provide a means of releasing air from the drip line when the system is turned on and can eliminate any air pockets.
2.They allow air to freely enter the system when it is shut down, ensuring a vacuum does not draw debris into the drip line via the drip emitter outlets. This condition is known as "suck back". Suck back can cause the drip line to collapse or draw in dirt and debris that clog the drip emitters.
To install an air relief valve, ensure you have a 17 mm x 1/2" FNPT tee at the start of your system (for 1/2" .700 OD drip tubing systems, use adapter tee LF307 in conjunction with coupler A134; for 1/2" .620 OD drip tubing systems use adapter tee LF306 in conjunction with coupler A134). The air relief valve screws into the 1/2" FNPT of the barbed tee. The air relief valve connection is normally located near the pressure regulator assembly as this is often the highest point in the drip system or the center of the line. It is important to install the air relief valve at the highest point of the system layout to allow it to work correctly.