The City of Brentwood utilizes ground water and surface water to supply domestic water to about 20,000 service connections through approximately 344 miles of water mains. The ground water is pumped from the City's active ground water wells. Surface water originates from rivers within the Sierra mountain range; the water flows into the Sacramento and San Joaquin rivers, and into the Delta. The surface water is treated at the City of Brentwood Water Treatment Plant and the Randall Bold Water Treatment Plant. Brentwood residents receive a blend of surface and ground water from these sources.
In 2019 the City's wells supplied over 0.64 billion gallons of water. An additional 2.70 billion gallons were supplied from the City of Brentwood Water Treatment Plant and the Randall-Bold Water Treatment Plant. The City has multiple storage reservoirs located throughout the City that allow for the storage of water during low demand periods for use during peak demand periods by the City's water customers.