About the Water Use Efficiency Rule
When the Washington State Legislature passed the 2003 Municipal Water Law (MWL) to reform the state's water laws, it accomplished two things:
- Added flexibility in the use of municipal water rights to serve growing communities by eliminating some of the risk of losing those municipal rights to the state.
- In exchange for this water right flexibility, the law requires municipalities to use water efficiently.
Requirements
Water Use Efficiency requirements can be found in WAC 246-290 and in the May 2025 Revised Fourth Edition of the Guidebook 331-375 (PDF). To summarize, municipal water suppliers must:
- Publicly establish water savings goals for their customers.
- Evaluate or implement specific water saving measures to achieve customer-based goals.
- Develop a WUE planning program to support the established goals.
- Install meters on all customer connections by January 22, 2017.
- Achieve a standard of no more than 10% water loss.
- Report annually on progress towards achieving these goals.
What the Rule Achieves
Using water efficiently helps water systems protect against:
- Temporary water service interruptions during peak usage.
- Long-term or repeated water disruptions due to limited water supply.
- Contamination of the water supply due to leaky pipes.
The Water Use Efficiency requirements also:
- Help ensure reliable long-term water supplies.
- Promote good stewardship of the state's water resources.
- Ensure efficient operation and management of water systems.
- Reduce energy use and save money.
Who This Affects
Any Group A community water system that serves at least 15 residential service connections must comply with the Water Use Efficiency Rule, whether publicly or privately owned.