GPH Irrigation Products Spec-Check GPSTCV2 Green Threaded Emitter With Check Valve 2 GPH Flow Rate. The GPH Spec-Check GPST emitter is designed to perform in the harshest environments, bringing commercial grade ruggedness to drip irrigation while providing an unmatched CV ratio. This means they are turn key and maintenance free, no more call backs due to inconsistent flows from one emitter to another.