Sellerocity Pressure Washer 3/8" NPT Brass In Line Chemical Acid Chlorine Detergent Soap Fixed Injector 5-8 GPM 2.3 Orifice Chemical Injectors for pressure washers work on the downstream side of the pump and are activated when using the low pressure black spray nozzle. The fixed chemical injector always delivers the same rate of chemicals estimated at 20%. These chemical injectors are re-buildable and should be properly cleaned out by rinsing with water for up to two minutes.