As natural gas flows through pipes, it loses part of its pressure due to friction and resistance. The pressure drop must remain within acceptable limits for appliances to operate correctly.
Piping length
The longer the path, the greater the total pressure loss usually is.
Diameter
A smaller diameter increases flow velocity and losses.
Fittings
Elbows, tees, valves, filters, and other fittings add local resistance.
Flow rate
As consumption increases, losses also increase. This is why a network may operate correctly at low load but present problems at high load.
Conclusion
Proper sizing is based on calculation rather than just empirical diameter selection.
