Sorry, I don't have the gallons.
From the FoC&T Dispatch Nov 1992. Tank in use before 1883 with water rights conveyed in 11/29/1884. In 1884 1,000' of wrought iron pipe of 1", 1 1/2" and 2" diameter was laid for gravity flow from a spring. It went to a standard wooden tank with a 6" flow pipe built in 1884. The tank was replaced in 1931, presumed to be the smaller tank as it was photographed by Don Rogers 5/31/39. The tank was rebuilt by the C&TS in using redwood with the original framing in 1987.