Summary of Washington's Water Reuse Guideline or Regulation for Centralized Non-potable Reuse

This page is part of the EPA’s REUSExplorer tool, which summarizes the different state level regulations or guidelines for water reuse for a variety of sources and end-uses.
The source water for this summary is Treated Municipal Wastewater.

On this page:

• Technical basis
• Applications of centralized non-potable reuse approved for use in Washington
• Water reuse category/type
• Additional context and definitions
• Centralized non-potable reuse specifications (table)
• Upcoming state law or policy
• References
• Disclaimer

---

This page is a summary of the state’s water reuse law or policy and is provided for informational purposes only. Please always refer to the state for the most accurate and updated information. 

In Washington, centralized non-potable reuse centralized non-potable reuse The use of recycled water for centralized non-potable reuse where the water does not derive from the same site where it is to be reused. Can include, but is not limited to, toilet flushing, dust control, soil compaction, fire protection, commercial laundries, vehicle washing, street cleaning, snowmaking, and other similar uses. Excludes on-site non-potable water reuse and the use of recycled water for agriculture or landscaping. applications include toilet and urinal flushing and commercial or industrial laundry, among others. The source of water (treated municipal wastewater) treated municipal wastewater Treated wastewater effluent discharged from a centralized wastewater treatment plant of any size. Other terms referring to this source of water include domestic wastewater, treated wastewater effluent, reclaimed water, and treated sewage. is specified by the state as municipal wastewater. The write-up uses state terms when discussing sources or uses of water that may differ from the Regulations and End-Use Specifications Explorer's (REUSExplorer's) terms.

Technical basis

Washington approves the use of reclaimed water for centralized non-potable reuse applications including toilet and urinal flushing, laundry and commercial and institutional uses that have public contact, environmental contact or restricted access (Wash. Admin. Code § 173-219). All applicable provisions of the Clean Water Act (CWA) (33 U.S.C. §§ 1251 et seq.), including its implementing regulations, must be met in addition to any state water quality standards. In Washington, no reclaimed water may be distributed or used without a state-issued reclaimed water permit (Wash. Admin. Code § 173-219; Wash. Rev. Code § 90-46). Class A and Class B water are used for centralized non-potable reuse applications and each class has varying treatment requirements. The technical basis for the removal of chemical and microbial contaminants is not explicitly specified.

Applications of centralized non-potable reuse approved for use in Washington

Wash. Admin. Code § 173-219 defines the following approved centralized non-potable reuse applications:

• Toilet and urinal flushing or laundry in commercial or industrial facilities, buildings, apartments, condominiums, hotels and motels (Class A)
• Commercial and institutional uses (including public water features) with public contact (Class A)
• Commercial and institutional uses with environmental contact (Class B) 
• Commercial and institutional uses with restricted access (Class B)

Water reuse category/type

The various classes of reclaimed water treatment are defined by their respective treatment requirements and applicable performance standards. The respective treatment requirements are briefly summarized for centralized non-potable reuse applications: 

• Class A treatment must meet Class B requirements (secondary treatment including biological oxidation and disinfection). Disinfection methods include chlorine, UV or other disinfection methods that are in accordance with the most recent Criteria for Sewage Works Design (WA Ecology, 2022). Additionally, one of the following treatment process train requirements must be met:
  • Biological oxidation, followed by coagulation, filtration and disinfection, demonstrating at least a 4-log virus removal or inactivation.
  • Biological oxidation, followed by membrane filtration and disinfection, demonstrating at least a 4-log virus removal or inactivation.
  • Combination of biological oxidation and membrane filtration via a membrane bioreactor, followed by disinfection, demonstrating at least a 4-log virus removal or inactivation.
  • An alternative treatment method, that demonstrates to the satisfaction of the lead agency that it provides for equivalent treatment and reliability. 
• For Class B water, the treatment requirements are secondary treatment, including biological oxidation, followed by disinfection. Disinfection methods include chlorine, UV or other disinfection methods that are in accordance with the most recent Criteria for Sewage Works Design (WA Ecology, 2022).

Additional context and definitions

Washington defines reclaimed water as “water derived in any part from a wastewater with a domestic wastewater component that has been adequately and reliably treated to meet the requirements of this chapter, so that it can be used for beneficial purposes” (Wash. Admin. Code § 173-219). Commercial and institutional uses are defined as “non-potable uses of water to produce products, provide goods and services, or for associated sanitary uses such as toilet flushing. The term does not include land application or irrigation uses.” (Wash. Admin. Code § 173-219).

Class A and B municipal reclaimed water piping, valves, outlets, storage facilities and other appurtenances must be color-coded purple and the pipes must be at least 200 feet away from potable water intakes, including well-heads, springs, surface water or designated groundwater (Wash. Admin. Code § 173-219). The reclaimed water generator must notify the public and employees at the site of the reclaimed water (for all use areas) by posting advisory signs or distributing advisory notices. The signage must be purple-colored and read “Reclaimed Water – Do Not Drink”. 

Centralized non-potable reuse specifications

Summary of Washington's Centralized Non-potable Reuse Specifications

Source = Wash. Admin. Code § 173-219

^* Information about sampling and monitoring requirements such as frequency, site and quantification methods not specifically listed in the table was not explicitly specified in the State-specific regulations.  

^a Listed as 23 MPN/mL or CFU/mL in Wash. Admin. Code § 173-219.

^b Additional log reductions occur during drinking water treatment.

^c If chlorine was used as the disinfectant.

Upcoming state law or policy

No upcoming regulations pertaining to centralized non-potable reuse were found for Washington.

References:

Clean Water Act, 33 U.S.C. §§ 1251 et seq.

Reclaimed Water, Wash. Admin. Code § 173-219.

Reclaimed Water Use, Wash. Rev. Code § 90-46. 

State of Washington Department of Ecology (WA Ecology). 2022. Criteria for Sewage Works Design (Orange Book).

---

Disclaimers

Please contact us at [email protected] if the information on this page needs updating or if this state is updating or planning to update its laws and policies and we have not included that information on the news page.