One well serving two residences is considered a Group B public water supply, but is placed in a separate classification as it has a different set of regulations than those with 3 or more connections. Two-party water systems in Thurston County are regulated by the County Public Health and Social Services Department, Environmental Health Division (Health Dept).

Water System Approval Process

Find out the steps to getting a 2-party water system approved by the County. ...more

Rules and Regulations

• Article III [PDF] — Thurston County Health Code
• WAC 246-291 — Washington Administrative Code

Recommendations

1. The pump should be capable of producing a minimum of 17 gpm. A minimum 30 psi at maximum demand should be supplied to each property line or residence.
   
2. The pressure tank(s) should be sized so that the drawdown provides adequate pump protection and/or storage.
   Pump protection: 2.5 x pump rate = gallons. (This is the minimum drawdown capacity of the tank.)
3. Prior to use, the newly constructed system should be disinfected with a chlorine dosage of no less than 10 parts per million (ppm) as measured after a contact time of 24 hours (10 ppm is equivalent to approximately 1 quart chlorine bleach per 1,000 gallons water).
4. On-going water quality monitoring: One bacteriological analysis per year and one nitrate analysis every three years is recommended.
5. It is recommended that an operation and maintenance agreement be established between parties. Examples are available upon request.
   

NOTE: Expansion of a two-party system to provide additional connections will require that the system meet all public water system requirements of the Thurston County Sanitary Code, Article III [PDF]. This includes a design of the proposed system expansion by a qualified water system designer or engineer and subsequent approval by the Health Dept. For additional information, see Group B or 2-Party Water System Design Supplemental Application [PDF].

Water Testing

It is recommended that 2-party systems test for coliform bacteria every 12 months and nitrate every 36 months. For information on the Thurston County lab, see Water Quality Lab. To view a list of other certified testing facilities in Washington, see the Dept of Ecology Accredited Lab List [PDF].

Applications and Forms (all applications, forms and guidelines are in PDF format)

The following are frequently used Group B water system forms:

• Well Site Inspection (2-Party, Group B, or Group A)
  (both Supplemental and Master Applications required)
• Supplemental Application (Guidelines)
• Master Application (Guidelines)
• Water System Design
  (both Supplemental and Master Applications required)
• Supplemental Application (Guidelines)
• Master Application (Guidelines)
• Locating or Recreating a Water Well Report Fact Sheet
• Covenants
• Declaration of Covenant
• Public Water Source (Note: legal-sized paper needed)
• Non-Public Water Source (Note: legal-sized paper needed)
• Covenant Fact Sheet
• Restrictive Covenant
• Public Water Source (Note: legal-sized paper needed)
• Non-Public Water Source (Note: legal-sized paper needed)
• Covenant Fact Sheet
• Well Construction/Decommissioning Application (Guidelines)
• Operation & Maintenance Agreement Sample Form
• Certification of Inspection and Installation of Two-Party Water System Projects
• Certificate of Water Availability (COWA) — Connection to a Single Family or Two-Party Water System
• Priority of Service Application - Water System