Protect Your Groundwater When You Chemigate

Back to Chemigation Initiative
Back to Educational Materials

Do you inject pesticides into your irrigation system? If so, then the California Department of Pesticide Regulation would like to remind you that safety devices are required to prevent groundwater contamination.

Groundwater Contamination Can Occur If:

  • Irrigation water containing chemicals flows back into the well
  • The chemical injection pump continues to run after shut down of the well pump
  • Chemicals overflow from the chemical supply tank onto surrounding soil

Prevention is the Key to Protection

Prior to injecting any pesticide, read the label to check if it can be applied through an irrigation system and then check for required backflow prevention components (A-H) that prevent backflow of a pesticide to a private well. Please contact your Agricultural Commissioner (California Department of Food and Agriculture page opens in a new browser window) for additional requirements or designs that comply.


bluebar Read all chemigation instructions on the label before injecting the chemical

bluebar Identify all components of your system and make sure they are functioning properly

bluebar Monitor your system during chemigation

Required Chemigation Components

Chemigation system with required safety devices

(A) Mainline Single Check Valve
(B) Low Pressure Drain
(C) Air/Vacuum Relief Valve
(D) Pressure Switch
(E) Interlocking System Controls
(F) Solenoid Operated Valve
(G) Chemical Injection Pump
(H) Injection Line Check Valve

Component Descriptions

abar (A) Mainline Single Check Valve:

  • Prevents backflow to well
  • Spring-loaded, positive closing action
  • Watertight seal (not metal to metal)
  • Install between well & chemical injection line

bbar (B) Low Pressure Drain:

  • Drains minor check valve leakage away from well
  • Install at bottom side of irrigation pipeline, upstream of mainline check valve

cbar (C) Air/Vacuum Relief Valve:

  • Prevents backsiphonage
  • Can be combined with inspection port
  • Install upsteam of mainline check valve

dbar (D) Pressure Switch:

  • Stops well pump when water pressure decreases
  • Install in irrigation pipeline or well pump

ebar (E) Interlocking System Controls:

  • Automatically shuts off chemical injection pump when well pump stops
  • Solenoid valve & chemical injection pump interlocked with well pump
  • Install between chemical injection pump and well pump

fbar (F) Solenoid Operated Valve:

  • Prevents chemical withdrawl when irrigation system shuts down
  • Install on intake side of chemical injection pump & connect to interlocking system controls

gbar (G) Chemical Injection Pump:

  • Assures proper chemical injection rate
  • Constructed of chemically resistant materials
  • Connect to interlocking system controls

hbar (H) Injection Line Check Valve:

  • Prevents flow of fluid back towards chemical injection pump
  • Automatic, quick-closing check valve
  • Constructed of chemically resistant materials
  • Install between irrigation pipeline & chemical injection pump

Back to Diagram

If your well is connected to a municipal water system, contact your local health department to assure compliance.

Check with your Agricultural Commissioner (California Department of Food and Agriculture page opens in a new browser window) for additional components or designs that fulfill backflow prevention compliance.

Contact Information:
California Department of Pesticide Regulation
California Environmental Protection Agency
1001 I Street; PO Box 4015
Sacramento, CA 95812-4015
Phone (916) 324-4100; Fax (916) 324-4088