Protecting Public Health and the Environment.

Public Water System Classifications

The Idaho Rules for Public Drinking Water Systems require that DEQ classify all community, nontransient noncommunity, and surface water public drinking water systems  with a treatment and/or distribution classification based on indicators of potential health risk. Criteria used to determine the potential health risks include the system's complexity, size, and source water for treatment facilities; complexity and size of distribution systems; and other criteria deemed appropriate. Systems are classified by type (treatment or distribution) and class. Classifications range from Very Small to Class I, II, III, or IV. The rules also require that public drinking water systems be staffed by licensed operators based on the system classification.

Determining a System's Classification

Each public water system’s owner must calculate the system's treatment and/or distribution classification to ensure its operators, and in particular, the responsible and substitute responsible charge operators, are properly licensed.

Distribution System Classification

Based on complexity and population served as follows:

  • Very Small Water System (VSWS)  * see definition below
  • Distribution Class I - 501 to 1,500 (DWD1)
  • Distribution Class II - 1,501 to 15,000 (DWD2)
  • Distribution Class III - 15,001 to 50,000 (DWD3)
  • Distribution Class IV - 50,001 and greater (DWD4)

* Very Small Public Drinking Water System A community or nontransient non-community public water system that serves 500 persons or less and has no treatment other than disinfection ** or has only treatment, which does not require any chemical treatment, process adjustment, backwashing or media regeneration by an operator. (e.g. calcium carbonate filters, granular activated carbon filters, cartridge filters, ion exchangers.)

** Disinfection – Introduction of chlorine or other agent or process approved by DEQ, in sufficient concentration and for the time required to kill or inactivate pathogenic and indicator organisms.

Treatment System Classification

Based on a point matrix associated to population, primary source type, and treatment processes associated to public water system treatment plants that are tracked in DEQ’s Safe Drinking Water Information System (SDWIS):

  • Treatment Class I – 0 to 30 points (DWT1)
  • Treatment Class II – 31 to 55 points (DWT2)
  • Treatment Class III – 56 to 75 points (DWT3)
  • Treatment Class IV - 76 points and greater (DWT4)


A worksheet has been developed to assist the owner of a public water system in determining system classifications. System classifications need to be reviewed at least every 5 years or any time a substantive change or upgrade is made to the treatment or distribution system (IDAPA The public water system’s regulating agency representative (DEQ or Health District) must be notified of any changes that would affect the system’s classification.

Two options (New or Existing systems):

New system owners need to complete the following blank classification worksheet:

Existing system owners need to review the following automated classification worksheet:

Once a public water system’s information has been placed into the Drinking Water Bureau’s database, system classifications will automatically be generated through this “System Classification Worksheet” application.

Please review and notify your DEQ or health district representative if changes to the System Classification worksheet information are needed.

Current Public Drinking Water System Classifications

DEQ updates a list of drinking water treatment and distribution system classifications daily.

Note: This list is a snapshot in time according to the date shown on the list.

Drinking Water System Name/Address Changes

The drinking water system owner or the owner's designee can add a contact or update address, telephone number, or e-mail information by using the "Change Water System Information" button on the PWS Switchboard.

Staff Contacts

Drinking Water Compliance Supervisor
Brandon Lowder
DEQ Boise Regional Office
1445 N. Orchard St.
Boise, ID 83706
(208) 373-0568

Drinking Water Compliance Supervisor
Anna Moody
DEQ Coeur d'Alene Regional Office
2110 Ironwood Parkway
Coeur d'Alene, ID 83814
(208) 666-4612

Senior Water Quality Engineer
Jacqueline Groarke
DEQ Idaho Falls Regional Office
900 N. Skyline Drive, Suite B
Idaho Falls, ID 83402
(208) 528-2688

Drinking Water Compliance Officer
Trina Burgin
DEQ Pocatello Regional Office
444 Hospital Way, #300
Pocatello, ID 83201
(208) 236-6160

Drinking Water/Wastewater Manager
DEQ Twin Falls Regional Office
650 Addison Avenue West, Suite 110
Twin Falls, ID 83301

Drinking Water Compliance Officer
Justin Walker
1118 F St.
Lewiston, ID 83501
(208) 799-4892

Other Contacts

State Rules

Related Pages

Public Water Systems in Idaho

Public Water System Switchboard

Public Water System Supervision Requirements

Drinking Water Operator Resources