A grooved lock coupler for holding a tee to a flow line for forced air conveyance and unloading of dry bulk granular material from a storage container vehicle is disclosed which comprises a tee having a first end, a second end, an inlet end, and a circumferential groove provided on the first end and a coupler for interconnecting to a flow line from the tee, the coupler having a cam lock fastener pivotally mounted on the coupler, the cam lock fastener cooperating with an opening in the coupler proximate the fastener to allow for the cam lock to extend through the opening in the coupler and to engage within the groove to lock the flow line and coupler to the tee in preparation for an unloading process.