San Francisco Fire Department Auxiliary Water Supply System

The Auxiliary Water Supply System (AWSS, though often referred to on manhole covers and hydrants as HPFS for High Pressure Fire System) is a high pressure water supply network built for the city of San Francisco in response to the failure of the existing emergency water system during the 1906 earthquake. Most damages to the city from the earthquake were caused not by the seismic event but by the fires that ensued, destroying 80% of the city's property value at the time. The improved water system was originally proposed by San Francisco Fire Department chief engineer Dennis T. Sullivan in 1903, with construction beginning in 1909 and finishing in 1913. The system comprises a collection of water reservoirs, pump stations, cisterns, suction connections and fireboats. While the system can use fresh or salt water, it is preferential not to use salt water, as it commonly causes galvanic corrosion in fire equipment.

The large, white oversized hydrants that are supplied by the AWSS/HPFS, of which there are 1,889, are visible throughout the city. The hydrants have painted tops that are color-coded as to their zone:

  • Black-topped hydrants are in the West of Twin Peaks zone and are fed by the Twin Peaks Reservoir.
  • Red-topped hydrants are in the upper zone and are fed by the Ashbury Street tank.
  • Blue-topped hydrants are in the lower zone and are fed by the Jones Street tank.
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