These 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 version of the chemical injector always delivers the same rate of chemicals estimated at 20%.  These chemical injectors are rebuildable and should be properly cleaned out by rinsing with water for up to two minutes.  This product is ISO 9000 Certified to ensure quality and consistency during the manufacturing process. This durable brass body venturi style chemical / acid injector has a simple and proven design for adjustable flow up to a maximum of 12%. Specs: 2.1 Oriface 3-5 GPM 4250 PSI Max  3/8" male x 3/8" male  Machined brass bar stock body with a proven design  Durability and unmatched quality at this price level  200°F - 4500 PSI stainless steel orifice