4.  PRESSURE
Delivering natural gas long-distance is impossible without pressure in the big mains. Starting from refineries in Texas and Louisiana, four large pipes, each as much as 42 inches (1,067 millimeters) in diameter, move the gas north. As communities tap into the line, the gas is compressed to maintain its pressure and the pipes grow smaller. By the time the gas enters a New York City stove it is traveling in a pipe only an inch (25 millimeters) wide.

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