Onsite Nonpotable Water Systems Rulemaking


The Department of Health (DOH) is considering adopting a new rule chapter (Chapter 246-275 WAC, Onsite Nonpotable Water Systems) to implement RCW 90.46.290 On-site nonpotable water systems.

This amendment to existing statute requires the department of health to estabish risk-based water quality standards for the onsite treatment of nonpotable alternative water sources for nonpotable end uses. In addition, it requires establishment of construction standards to achieve these water quality standards. The CR-101 Preproposal Statement of Inquiry (PDF), announcing our intention to begin rulemaking, was filed on August 9, 2021 and recorded as WSR 21-17-040.


The Onsite Nonpotable Water Systems (ONWS) rule would apply to multifamily residential, commercial, and mixed-use buildings, and district-scale projects, including a mix of multifamily residential, commercial, and mixed-use buildings. Alternative water sources include wastewater from all domestic fixtures, gray water, rainwater, stormwater, foundation drainage, and AC condensate. Water treated to the established risk-based water quality standards may be used for end uses such as toilet and urinal supply water, clothes washing, irrigation, and dust suppression.

Rule contents would include:

Rule Advisory Committee and Stakeholder Engagement

DOH is engaging in collaborative rulemaking in consultation with impacted agencies and stakeholders, including the Washington State Department of Ecology, Washington State Building Code Council, and Washington State Department of Labor and Industries. Other stakeholders we will invite to participate in the ONWS Rule Advisory Committee (RAC) include representation from the Washington State Association of Plumbers and Pipefitters, a local health jurisdiction, a local government currently operating a ONWS, and a design consultant.

Model Code

A model code that will be considered during this effort was developed by the National Blue Ribbon Commission for Onsite Nonpotable Water Systems. View the model regulation on the US Water Alliance's website.

Rule Advisory Committee (RAC)

DOH held two RAC meetings in October 2021. Based on feedback from the RAC, we are drafting rule language. A main concern of the RAC members was local capacity to implement the rule. DOH is working hard to find ways to address this issue. We intend to hold a third RAC meeting in April to get feedback from the RAC draft rule language.

Once we have addressed RAC feedback and updated the draft rule, we will share the draft language more broadly and hold an informal comment period. This will give stakeholders and interested parties not on the RAC an opportunity to provide their feedback and thoughts on the draft rule. This feedback is essential to write an implementable rule that protects public health and the environment.

October 12 RAC Meeting Presentation Slides (PDF)

October 28 RAC Meeting Presentation Slides (PDF)

Stay Informed

Rulemaking notices will be sent to various general interest and environmental public health lists. To receive notices, sign up for the Onsite Nonpotable Water Systems Rulemaking email list.

Rulemaking Contacts

Steve Deem, subject matter expert, 360-878-7625

Mamdouh El-Aarag, subject matter expert, 509-329-2148

Jocelyn Jones, project co-manager, 360-236-3020

Brian Sayrs, project co-manager, 509-329-2112