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Fire Hydrant Flushing

A hydrant flushing program is very important to water quality.  Over time, various materials such as corrosion products and organic materials, build up in the mains of municipal water distribution systems.  This buildup can cause water quality issues such as unusual tastes and odors and discoloration of the water.  Hydrant flushing programs are instituted by municipalities to flush the buildup out of the mains.  In a traditional hydrant flushing program, hydrants are opened one at a time in a general area, which increases the velocity of water in the mains.  The increased velocity picks up sediment that has settled in the bottom of the main and lightly scours the walls of the pipe to remove residue, which is then carried out the open hydrant(s).  The hydrants are left open until the water runs clear. 

A hydrant testing program ensures that hydrants are in full working order and verifies their flow capacity.  The following are inspected and tested:

  • Static pressure: available water pressure
  • Residual pressure: available water pressure that is left over during flow
  • Flow pressure: pressure that is flowing
  • Flow rate: gallons per minute of flow achieved
  • Caps: all hydrant port caps are removed and the threads greased
  • Ease of operation: hydrants that are difficult to operate are noted
  • Accessibility: landscaping that obstructs access to hydrants is noted

All noted defects or problems are reported to the Water Division for corrective action.  Test results are recorded and tracked with the City’s GIS system.  Areas within the water distribution system that demonstrate low fire flows are investigated and corrected by spot repairs if needed or system improvements incorporated into the Water Distribution Capital Improvement Program.  Per the City’s GIS data, there are 1,715 hydrants in the Highland Park system. 

Hydrant Flushing FAQs