Sometimes it looks like the Town of Hillsborough staff is just pouring water down the storm drains; however, there are reasons why the Hillsborough Department of Public Works must open fire hydrants:
To maintain water quality.The disinfectant chloramine becomes less effective as water collects at dead end lines and becomes old. The Town must therefore flush hydrants in areas where there is low water demand.
To clean water mains. Over time, small particles of rust and clay build up inside the Town's main water pipes, and can harbor colonies of bacteria that may harm water quality. Water quality staff use unidirectional flushing to pull water at a high velocity from a specific point in the system to a discharge point. The rapid movement of water scours the insides of the pipes. Often, the water will appear brown as it flows from the hydrant, but clears up after some time. Over the years, Hillsborough has greatly reduced the amount of water used in these unidirectional flushing procedures by regularly maintaining the pipes.
To conduct fire flow tests. Each fire hydrant must be tested periodically to ensure and document proper functioning in case of an emergency. Hillsborough must test the flow of its hydrants much more often than neighboring cities because it is a hilly community - the Town must ensure that its hydrants at high elevations have sufficient pressure to fight fires.
What happens during a flushing operation? During the flushing procedure, water flows out from hydrants, onto the street, and into storm drains. Residents can still use water normally throughout the flushing process. However, there may be small pressure fluctuations or minor aesthetic effects like cloudy or discolored water. This is not dangerous; running a faucet outside of the house or running cold water inside the house for a few minutes should resolve the problem. Please refrain from doing laundry during this period. Residents who experience continued water quality problems should call the Public Works Department at 375-7546. To report a water quality problem after hours, please call the Police Department at 375-7470.
Conserving water used in flushing operations
In an effort to conserve water, the Town of Hillsborough has altered some of its flushing practices. The Town has made significant capital investments to eliminate dead end lines in the system and thus reduce the need for water quality flushing. Furthermore, the Town combines fire flow and water line flushing activities where possible to reduce water use during dry seasons.
The Town continues to research water-conserving technologies for flushing operations.
Flushing operations are conducted Monday through Thursday, from 8:00 a.m. to 3:00 p.m. The flushing crews will set out signs notifying residents if flushing operations will be conducted in the area. If your clothes have become stained as a result of using water during a flushing operation, please keep them wet. You can call the Public Works Department, at 375-7546 to receive a cleaning agent to remove the stain at no charge.
The Town of Hillsborough1600 Floribunda Avenue, Hillsborough, CA 94010 (650) 375-7400
In an effort to conserve water, the Town of Hillsborough has altered some of its flushing practices. The Town has made significant capital investments to eliminate dead end lines in the system and thus reduce the need for water quality flushing. Furthermore, the Town combines fire flow and water line flushing activities where possible to reduce water use during dry seasons. 
