Main Cleaning

The 2020 Water Main Cleaning Program has Concluded for the Year

Thank you to the citizens of Fremont, Newark and Union City for your support of this important program. The main cleaning program has concluded for the 2020 calendar year and will resume in January 2021.  Please check our website toward the end of 2020 for additional information.


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 will remain safe for household uses such as drinking and cooking. You should, however, minimize water use and avoid washing light-colored laundry from 7:00 a.m. to 4:00 p.m. on the day or week main cleaning is scheduled for your neighborhood.

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. In order to clean our mains and continue to ensure high quality water for our customers, we need to flush at very high  flow rates that are not possible to recapture. The amount 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.