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Help Center
Main Cleaning
How We Clean
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.

Helpful Tips for Home
To minimize discolored water: 
  • Refrain from water use while main cleaning is in progress in your neighborhood. 
  • Wait an hour after street operations have ceased before using your taps to let normal flow patterns re-establish themselves.
  • To clear discolored water from your plumbing: 
  • Run the cold water faucet of your bathtub or other unscreened tap for 2-3 minutes until the water runs clear. 
  • If the water does not clear, turn off your faucet and wait an hour before repeating the process.

You will be notified by postcard or through your property manager at least one week prior to any main cleaning taking place in your neighborhood.

More Information
For more information on what to do if you are experiencing discolored water, please refer to our Discolored Water FAQs or call our Operations Department at (510) 668-6500.