There are brick circles at certain intersections scattered around the city. I used to think these had something to do with the old Cable Car lines but it turns out hey are water cisterns built after the 1906 earthquake. Are these cisterns still in use or are they empty?
According to the SFFD, the cisterns are part of SF’s Auxiliary Water Supply System, and still “remain in service for our use in the event of a hydrant system failure.”
How do they work?
SFFD spokesperson Lt. Mindy Talmadge told me in an email, “the cisterns provide a supplemental source of water for fire suppression in the event that the domestic water system and/or the Auxiliary Water Supply System are unavailable or prove insufficient to fight a fire. The cisterns are stand-alone reservoirs that provide a highly reliable but limited quantity of water that may prove to be a crucial resource in the event of an earthquake that produces significant ground motion.”
The storage volumes of the cisterns range from approximately 75,000 gallons to 200,000 gallons.
How many are there, and who owns them?
There are about 177 cisterns, mostly located in the northeast quadrant of the City. They were maintained by the San Francisco Fire Department until July of 2010.
“The transfer of responsibility and property of the Auxiliary Water Supply System to the PUC was recently made in an effort to balance the SFFD Budget,” Talmadge said. “The cisterns are not connected to the AWSS piping/hydrant system.”
Do our modern day cisterns differ from those of yore?
“The cisterns installed in the late 1800’s and early 1900s were constructed of brick, while a majority of the later construction is of reinforced concrete,” Talmadge said.
Read “well-known fire insurance underwriter” Rolla Watt’s original 1907 plan for the cisterns here. You can also read more cistern history at Atlas Obscura.
Photo: Nick Sherman via Atlas Obscura
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