How the Main Cleaning Program Works

ACWD cleans water mains to remove the buildup in pipes that may cause discolored water. This is accomplished by opening fire hydrants. As the water flows at high velocities through the mains, scale and fine sediment are dislodged. The resulting discolored water leaves the distribution system through the open fire hydrants. Since some of this water eventually flows into San Francisco Bay, ACWD utilizes disinfectant and sediment removal best management practices to minimize impacts to the environment.

Main cleaning may result in a brief period of discolored tap water for some Tri-City residents from January-June. Despite its appearance, the water remains safe for household uses such as drinking and cooking. ACWD recommends minimizing water use and avoid washing light-colored laundry from 7:00 AM to 4:00 PM on the day or week main cleaning is scheduled for your neighborhood.  

For additional information, please visit or contact the Operations Department administrative group at (510) 668-6500, Monday through Friday, 8:00 AM to 5:00 PM.