- (1) A person shall not serve as a human interlock for chemigation equipment.
- (2) A person with knowledge of the operation of both the irrigation and injection systems may function as a system interlock during fertigation: Provided that the person remains on-site to continuously monitor the application and is immediately available to terminate the application in the event of any equipment malfunction.
(3) Solenoid and check valve.
- (a) The chemical injection line must contain either a normally closed solenoid-operated valve connected to the system interlock or a normally closed hydraulically operated valve that opens only when the main water line is adequately pressurized. A normally closed, solenoid-operated valve must be placed on the intake side of the injection pump, immediately adjacent to the application tank.
- (b) The chemical injection line between the application tank and the metering device must contain an automatic, quick-closing check valve to prevent the flow of liquid back toward the application tank. The check valve must be placed immediately adjacent to the venturi chemical inlet.
[Statutory Authority: RCW 17.21.030, 15.58.040(2), and 15.54.800(2). WSR 25-22-066, s 16-202-355, filed 10/31/25, effective 12/1/25.]