eli5 How does the SFFD Auxiliary Water Supply System work, and how is it different than other systems built in the early 1900’sv

Question

The Three tiered Water reservoir system of Twin Peaks, Ashbury and Jones street, was built after the 1906 earthquake inspired by water systems around the world by Dennis T. Sullivan. How does it work and how is it unique to other similar “emergency backup water supply’s”

In: Technology