WAC 16-202-2012

What alternative methods may be used to prevent backflow into or seepage from application tanks?

Alternative technology used for backflow prevention must be accomplished by system design to fulfill the provisions of this chapter.
(1) In lieu of a normally closed solenoid with the injection system.
(a) A normally open valve must be located in the chemical injection line between the application tank and a positive displacement injection pump. The normally open valve must be spring-loaded, and must close upon a vacuum and open at atmospheric pressure. It must be elevated at least twelve inches above the maximum fluid level in the application tank and must be the highest point in the injection line.
(b) The mechanism described in (a) of this subsection cannot be used in conjunction with a venturi injection system.
(2) In lieu of a 10 psi opening (cracking) pressure check valve.
(a) An automatic, quick-acting, spring-loaded check valve must be attached at or positioned immediately adjacent to the injection point to prevent irrigation water from entering the chemical injection line.
(b) A normally closed solenoid must be installed immediately adjacent to the product outlet on the application tank. If electric, it must be interlocked with the injection pump or, if hydraulic, with the irrigation system.
(c) In place of (b) of this subsection, a normally open valve must be located in the chemical injection line between the application tank and a positive displacement injection pump as described in subsection (1)(a) of this section. This alternative cannot be used with venturi injection systems.
[Statutory Authority: Chapters 15.54, 15.58, and 17.21 RCW. WSR 01-13-063, § 16-202-2012, filed 6/18/01, effective 11/9/01.]