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REQUIRED CHEMIGATION SAFETY DEVICES

Equipment Required on the Irrigation Pipeline

Chemigation system with required safety devices

(A) Check Valve
(B) Low Pressure Drain
(C) Air/Vacuum Relief Valve
  Alternative for (A), (B), and (C):
   Gooseneck Pipe Loop
(D) Pressure Switch
   
Required Power and System Interlocks
(E) Interlocking System Controls
   
Equipment Required on the Injection Line
(F) Solenoid Operated Valve
  Alternatives:
  a. 10-psi Check Valve*
  b. Hydraulically Operated Valve
  c. Vacuum Relief Valve*
(G) Chemical Injection Pump
  Alternative: Venturi Injector
(H) Injection Line Check Valve**

* Device cannot be used with the Venturi Injector
** Device not required if a 10-psi Check Valve is used as an alternative to the Solenoid Operated Valve

Equipment Required on the Irrigation Pipeline

To prevent backflow of pesticide residues to the water source, pesticide labels state, "the system must contain a functional check valve, vacuum relief valve, and low pressure drain, PDF (142 kb) appropriately located on the irrigation pipeline to prevent water source contamination from backflow." These devices must be installed in the following manner.
  • A. The check valve must be installed between the water source and the injection point.
  • B. The low pressure drain must be installed upstream of the check valve to dispose of small volumes of fluid which may leak past the check valve.
  • C. The vacuum relief valve, or combination air and vacuum relief valve, must be installed upstream of the check valve to prevent the formation of a vacuum which could cause backsiphonage.

    Irrigation line check valve, vacuum relief valve, and low pressure drain Click on photo to enlarge image - Irrigation line check valve, vacuum relief valve, and low pressure drain

    Alternative Device for (A), (B), and (C):

    • A gooseneck pipe loop located in the main water line immediately downstream of the irrigation water pump. The bottom side of the pipe at the loop apex must be at least 24 inches above the highest sprinkler or other type of water emitting device in the field. The loop must contain a vacuum relief valve (or combination air and vacuum relief valve) at the apex of the pipe loop. The pesticide injection port must be located downstream of the apex of the pipe loop and at least 6 inches below the bottom side of the pipe at the loop apex.

  • D. To help ensure the efficiency of the chemigation, pesticide labels state, "the irrigation line or water pump must include a functional pressure switch, PDF (144 kb) which will stop the water pump motor when the water pressure decreases to the point where pesticide distribution in adversely affected." The pressure switch must be installed downstream of the irrigation pump to identify pressures too low for proper pesticide application or low pressure conditions signifying irrigation pump failure.

    Pressure switch Click on photo to enlarge image - Pressure switch

Required Power and System Interlocks
  • E. To automatically stop the pesticide application if there is a loss of pressure or if the irrigation pump stops, the pesticide label states, "the system must contain functional interlocking controls, PDF (160 kb) to automatically shut off the pesticide injection pump when the water pump motor stops."
    • The system must interlock the normally closed solenoid or hydraulically operated valve with the metering pump or Venturi bypass booster pump so that the valve closes upon shut down of the injection pump or Venturi bypass booster pump.
    • It must also interlock the normally closed solenoid or hydraulically operated valve with the pressure switch so that the valve opens only when the main irrigation line is adequately pressurized.

Equipment Required on the Injection Line

  • F. The pesticide injection pipeline must also contain a functional, normally closed, solenoid-operated valve, PDF (140 kb) located on the intake side of the injection pump and connected to the system interlock to prevent fluid from being withdrawn from the supply tank when the irrigation system is either automatically or manually shut down." Several alternatives to this device are listed below.

    Normally closed, solenoid-operated valve Click on photo to enlarge image - Normally closed, solenoid-operated valve

Alternative Devices for the Solenoid-Operated Valve:

  • a. Functional spring-loaded check valve with a minimum of 10 pounds per square inch (psi) cracking pressure, PDF (133 kb).
    • This alternative is appropriate for only those chemigation systems using a positive displacement injection pump and is not for use with Venturi injection systems.
    • This device must prevent irrigation water under pressure from entering the pesticide injection line and must prevent leakage from the pesticide supply tank on system shutdown.
    • It must be constructed of pesticidally resistant materials.
    • This single device can substitute for both the solenoid-operated valve and the functional, automatic, quick closing check valve in the pesticide injection line.

    10-psi injection line check valve Click on photo to enlarge image - 10-psi injection line check valve

  • b. Functional normally closed, hydraulically operated check valve, PDF (150 kb).
    • The control line must be connected to the main water line such that the valve opens only when the main water line is adequately pressurized.
    • This device must prevent leakage from the pesticide supply tank on system shutdown.
    • It must be constructed of pesticidally resistant materials.

    Normally closed, hydraulically operated check valve Click on photo to enlarge image - Normally closed, hydraulically operated check valve

  • c. Functional vacuum relief valve, PDF(161 kb) located in the pesticide injection line between the positive displacement pesticide injection pump and the check valve.
    • This alternative is appropriate for only those chemigation systems using a positive displacement pesticide injection pump and is not for use with Venturi injection systems.
    • This device must be elevated at least 12 inches above the highest fluid level in the pesticide supply tank and must be the highest point in the injection line.
    • It must open at 6 inches water vacuum or less and must be spring loaded or otherwise constructed such that it does not leak on closing.
    • It must prevent leakage from the pesticide supply tank on system shutdown.
    • It must be constructed of pesticidally resistant materials.
  • G. To inject the pesticide into the irrigation line, pesticide labels state, "systems must use a metering pump, PDF (143 kb), such as a positive displacement injection pump (e.g., diaphragm pump) effectively designed and constructed of materials that are compatible with pesticides and capable of being fitted with a system interlock." However, the Venturi injector may be used in place of the metering pump and has specific requirements listed in the next section.

    Pesticide metering pump Click on photo to enlarge image - Pesticide metering pump

  • H. The pesticide injection pipeline must contain a functional, automatic, quick-closing check valve, PDF (132 kb) to prevent the flow of fluid back toward the injection pump." This device prevents the irrigation water from overflowing the pesticide tank.

    Injection line check valve Click on photo to enlarge image - Injection line check valve

Alternative Device to a Metering Pump:

A Venturi injector may be used in place of the metering pump and may be inserted (1) directly into the main irrigation line, (2) into a bypass line, or (3) into a bypass line with an auxiliary booster water pump.

  • Auxiliary booster water pumps must be connected with the system interlock such that they are automatically shut off when the main line irrigation pump stops or in cases where there is no main line irrigation pump, when the water pressure decreases to the point where pesticide distribution is adversely affected.
  • Venturi systems must be constructed of pesticidally resistant materials.
  • The line from the pesticide supply tank to the Venturi must contain a functional, automatic, quick closing check valve to prevent the flow of the liquid back toward the pesticide supply tank. This valve must be located immediately adjacent to the Venturi pesticide inlet.
  • This same supply line must also contain either a functional normally closed solenoid-operated valve connected to the system interlock or a functional normally closed hydraulically operated valve which opens when the main water line is adequately pressurized.
  • In bypass systems, as an option to placing both valves in the line from the pesticide supply tank, the check valve may be installed in the bypass immediately upstream of the Venturi water inlet and either the normally closed solenoid or hydraulically operated valve may be installed immediately downstream of the Venturi water outlet.

1) Diagrams of Inline Venturi Systems (inserted directly into the main irrigation line):

     
   
  2) Diagrams of Bypass Venturi Systems with a Gate or Butterfly Valve (inserted into a bypass line):  
  Bypass Venturi with gate or butterfly valve  
   
  3) Diagrams of Bypass Venturi Systems with a Booster Pump (inserted into a bypass line with an auxiliary booster water pump):  
  Bypass Venturi with booster pump  
     

Summary

Proper equipment is the first step in complying with the safety requirements. The safety devices are effective in protecting the water supply, preventing pesticide spills and ensuring that injections only occur when the irrigation system is operating properly. Always check your local regulations to see if they exceed the requirements stated above.


Additional Information: