Add-It fertilizer injector, 1 gallon capacity, 1" FPT inlet/out ASAE award-winning Add-It fertilizer injector 1 gallon capacity with 1" FPT inlet/outlet (female pipe threads) Proportioning fertilizer injector - injection rate is constant A minimum of 5 GPM and 10 PSI is required to function Perfect for drip and conventional sprinkler irrigation systems