Introduced in 1808 in lower Manhattan, the fire hydrant hasn’t changed much technologically.9 From the large water mains running beneath the streets, smaller branch lines run up to hydrants. The hydrant houses a pipe and valves to access and regulate water flow. Many hydrants are painted with a number — typically 12 or 24, sometimes 48 — which indicates in inches the diameter of the pipe to which the hydrant is attached. This is an interesting clue as to what is going on beneath the sidewalk.
Hydrants are opened by removing a protective cap and rotating a valve nut. This allows water from the main to fill the hydrant’s barrel and ostensibly a fireman’s hose.10 In an unofficial uncapping, there is no hose — the water simply bursts from the hydrant once the main valve is opened.
The city has installed many systems to prevent unauthorized openings, from aluminum harness caps in the 1960s to the Hydralock in the 1980s. In 1993, the custodial lock, a steel cap that shuts off the main leading into the hydrant was introduced, prompting some DEP officials to claim, prematurely, that the tradition of opening hydrants was dead.11 Although a special wrench is needed to open any of these hydrants, people manage to borrow the tool or devise a way to defeat the locks so the hydrants continue to flow.
The DEP and fire department do provide for legal recreational use of a hydrant with a spray cap. Distributed free of charge by the fire department, a spray cap reduces a hydrant’s flow from 1000 gallons per minute to 25 gallons per minute through perforations in the cap.