Group A Transient Non-Community (TNC) Water Systems

Information on this page is geared to the specific needs of transient non-community (TNC) water system owners and operators to make their jobs easier and help them comply with federal and state requirements.

Transient non-community water systems provide drinking water to a population that changes day to day. They include, among others, campgrounds, hotels, rest areas, and restaurants with their own water supplies.

Group A Transient Non-Community water systems are regulated under Chapter 246-290 of the Washington Administrative Code.

TNC water systems serve:

  • Twenty-five or more different people each day for sixty or more days within a calendar year;
  • Twenty-five or more of the same people each day for sixty or more days, but less than one hundred eighty days within a calendar year; or
  • One thousand or more people for two or more consecutive days within a calendar year.

Group A TNC Water System Design Guidelines and Workbook

Group A Transient Non-Community Water System Design Guidelines 331-676 (PDF)
These guidelines explain how to design Group A-TNC water systems to ensure safe, adequate, and reliable drinking water for those the water system will serve. They will also help you prepare a complete Group A-TNC Design Workbook 331-677, linked below.

Group A TNC Water System Design Workbook 331-677 (Word)
Completing this fillable Workbook satisfies project report, design, and source approval requirements for a new or expanding Group A-TNC water system (WAC 246-290-110, -120, and -130, respectively). Useful information for completing this workbook is found in the Group A-TNC Water System Design Guidelines 331-676, linked above.

Monitoring Requirements

Monitoring requirements vary for TNC water systems depending on the system's characteristics. You can find your monitoring requirements for your particular system on-line in our water system Sentry Internet database. View or download your system's Water Facility Inventory (WFI) and water quality data. Look on page 2 of your WFI in sections 33 and 34 for your system's monitoring schedule for Coliform and Nitrates.

Example Only

Box 33. contains an example system's monitoring schedule for Coliform and box 34. shows an example Nitrate schedule for each active source. Download your most recent WFI from Sentry Internet database to see your requirements.

How to collect and submit Coliform and Nitrate samples to a certified laboratory:

Coliform Information and Public Health Advisory Packet

  • Coliform Information Packet: Materials to help you better understand total coliform bacteria. The packet contains information about what coliform is, how to test for it, and what to do if you find it in your water system.
  • Coliform Public Health Advisory Packet: Tools to help you respond to the presence of fecal contamination in your water supply. If you have fecal contamination in your system, the Department of Health will work closely with you to help resolve the situation and determine if a public health advisory is required.

Nitrate Public Health Advisory Packet

  • Nitrate Public Health Advisory Packet: Materials in this packet are designed to help you respond during times of high nitrate levels in your water supply. If you have nitrate contamination in your system, you will be working closely with the Department of Health to resolve the situation and make sure your customers are adequately notified.

Seasonal Start-Up and Shut-down Procedures


For More Information

If you need more information, contact your Regional Office. The Regional Office Map (PDF) outlines counties in each region.

Northwest Regional Office—Kent: 253-395-6750

Southwest Regional Office—Olympia: 360-236-3030

Eastern Regional Office—Spokane: 509-329-2100