Enter connected appliance load and pipe run to get the minimum pipe size for natural gas or LPG installations.
Add up all appliance MJ/h ratings
Typically 50–100 Pa for residential
For a 50 MJ/h connected load over a 15 m run with 50 Pa allowable pressure drop, a DN25 pipe is typically sufficient for natural gas. Enter your exact values in the calculator above.
Under NZS 5261, the allowable pressure drop from the meter to the most remote appliance is typically 50–100 Pa for low-pressure residential systems (1.125 kPa supply). Commercial systems may allow higher drops — check with the gas company.
The Spitzglass formula calculates gas flow capacity for low-pressure systems: Q = 0.0004 × √(ΔP × d⁵ / (sg × L)), where Q is flow in m³/h, ΔP is pressure drop in Pa, d is internal diameter in mm, sg is specific gravity, and L is pipe length in metres.