Unless standards are somehow different in California, fire hydrants are fed by a minimum 6" line; typically,
water mains that are looped through a neighborhood or around a large complex are required to be a minimum
of 8" diameter. "Dead end" lines are a minimum of 10" as well.
Off these mains come the 6" feeds for hydrants, which are typically spaced 250 feet apart (some jurisdictions
require less distance, some more) as well as "taps" for water service to residences, businesses and the like.
Such hydrant supplies, their spacing and their designs are such that they provide enough flow at a given minimum
pressure that's been determined in order to fight a fire of a given "hazard" - residential being considered a "light"
hazard (as per NFPA), for example.
What I'm saying here is that the whole system is intended for use fighting a single fire event - a house in the case of a
neighborhood for example, or a large structure in the case of a factory - not the whole damn world ablaze.
I have heard of sytems "cavitating" (running out of water) in which pumps trying to draw water from it actually cause
a suction (negative pressure) causing underground pipes to collapse.
I've only seen it a couple times, on isolated feed lines going to fire pumps - never a larger scale.
Such pumps don't care if their suction side goes negative, they'll keep trying to draw until they fail.
It is absolutely critical that a municipal water system be kept fully supplied with water, therefore - because in the end,
all such systems are never over-built, only built to a certain minimum set of rules (to curtail costs).
Stories of reservoirs being empty are truly frightening, for that means firefighting personnel go into hellish situations
not knowing that they may not have what they need to fight their way back out of them.
As many times as parts of California have been on fire, you'd hope they know a)eliminate the fuel for these fires if
possible and b)maximize efforts to be prepared to fight them when they occur.
It appears both are in short supply to this day - and honestly, there's no excuse for that out there.
)
