GWRS - new water you can count on

The GWRS is the world's largest water purification system for indirect potable reuse. The system takes highly treated wastewater that would have previously been discharged into the Pacific Ocean and purifies it using a three-step advanced treatment process consisting of microfiltration, reverse osmosis and ultraviolet light with hydrogen peroxide. The process produces high-quality water that meets or exceeds all state and federal drinking water standards.

View the GWRS technical brochure (PDF)

Reverse Osmosis Trains of the GWRS (Steve Crise, Courtesy of AWWA)

The process

After wastewater is treated at the Orange County Sanitation District, it flows to the GWRS where it undergoes a state-of-the-art purification process.

The process

UV lamp change

Frequently asked questions

You have questions? We have answers. Explore some of the GWRS' most frequently asked questions.

Frequently asked questions

tour group with Mehul Patel

Book a tour

Schedule an in-person or virtual tour of the Groundwater Replenishment System. 

Book a tour

GWRS Final Expansion groundbreaking

Final expansion

The GWRS Final Expansion project will increase treatment capacity from 100 to 130 million gallons per day; enough water for 1 million people!

Final expansion

GWRS is a joint collaboration between OCWD and OC San.

Orange County Water District Orange County Sanitation District