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.

Evaluation of Recapture Options
Prior to resuming the main cleaning program this year, ACWD staff thoroughly examined possible recapture methods for the main cleaning discharges and will continue to do so. As much as ACWD would like to be able to reuse water from the main cleaning program, unfortunately, in most cases, it's just not technically feasible. To clean our mains and continue to ensure high quality water for our customers, we need to flush at remarkably high flow rates that are not possible to recapture. The number of trucks, transit time for the trucks, gas, etc. needed to recapture the water would be excessive. Directing the water to a truck would be very time-consuming and resource intensive, significantly increasing costs of the State-required processes.