Gas Leak Equivalent Hole Diameter
The equivalent orifice (hole) diameter behind a measured gas leak rate.
Example
You enter
- Measured leak rate (ft³/hr) 3.15
- Upstream gauge pressure (psi) 0.25
- Gas natural_gas
- Discharge coefficient 0.7
You get
- Equivalent orifice diameter 0.05 in
- Orifice area 0.00196 in^2
Details, formula, and sources
d = sqrt( 4 Q / (3550 c pi sqrt(dP / SG)) ). A 3.15 cfh natural-gas leak at 0.25 psi with c 0.7 is about a 0.050 in hole. Turns a clocked or metered leak into a hole size. An estimate of the effective hole, not a code leak-test method; any leak is a hazard - find and repair it. Uses the gas orifice-flow form, not the water one.
d = sqrt( 4 Q / (3550 x c x pi x sqrt(dP / SG)) ), the inverse of Q = 3550 x c x (pi d^2 / 4) x sqrt(dP / SG); orifice area A = Q / (3550 c sqrt(dP/SG)).
Classical orifice-flow leak approximation (compressible small leak), solved for the diameter; the 3550 coefficient and gas specific gravity from public engineering references.
The orifice-flow leak relation is public; the gas specific gravity is a bundled property.
Estimate. AHJ and licensed plumber / gas fitter govern. Verify against the IPC / IFGC edition adopted in your jurisdiction.
Field names used by the API: leak_rate_cfh, upstream_psi, gas, c, orifice_diameter_in, orifice_area_in2
- Discharge coefficient c about 0.7 for a sharp orifice unless the user supplies otherwiseengineering practice
- Gas specific gravity bundled natural-gas / propane specific gravityengineering reference
- Estimate only the small-leak orifice approximation, not a code leak-test methodscope of this tile