alt Hacker News> During a fire in the Bronx, firemen laid 7,000ft of hose to get to a suitable water supply and the truck pumped as though it was dipping its feet into the ocean.
"7000 ft" sounds wrong to me. That's over a mile of hose. Feels like that's unnecessarily long. I'd love to learn more about this. Anyone know when or what fire this was?
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If they were all in a single line it probably wouldn't have worked -- series hydrodynamic hose impedance adds just like series resistance in a circuit and the pressure at the end would have been too low to be useful. But if it was 7000 feet arranged in several shorter parallel lines it's possible.
It could draw from 8 hydrants. So average of 900 feet in that case.
Which still seems like a lot, but not so incredible.
The article mentions that the main pumping unit could draw water from 8 hydrants at once. So 7000 ft of total hose to get to 8 hydrants sounds like it makes sense.
I wonder if maybe it can't even use hydrants that are too near each other in the plumbing graph.