Formula & worked example
Q=m/ρ; D=sqrt(4Q/(πv)).
5,000 kg/h condensate at 950 kg/m³ and 1.5 m/s needs about 35 mm minimum internal diameter before schedule selection.
Plant engineering calculator · Updated Sep 17, 2026
Condensate Pipe Sizing Calculator — Flow, Velocity & Diameter
Size a liquid condensate return line from mass flow, density and target velocity. Returns required internal diameter, volumetric flow and practical velocity checks in SI and US units.
Inputs
Live result
Volumetric flow 5.263158 m³/h
Minimum ID 35.22746 mm
Minimum ID 1.386908 in
Target velocity 1.5 m/s
Target velocity 4.92126 ft/s
Assumptions & limits
- This liquid-line screening model does not size two-phase flash-steam return lines.
- Select the next suitable commercial pipe ID and recheck velocity and pressure loss.
Frequently asked questions
What does this Condensate Pipe Sizing Calculator calculate?
Size a liquid condensate return line from mass flow, density and target velocity. Returns required internal diameter, volumetric flow and practical velocity checks in SI and US units.
Can I use the result for final equipment selection?
Use it for screening, benchmarking and option comparison. Final selection should use measured conditions, manufacturer performance data and applicable engineering standards.
Why are assumptions shown beside the calculation?
Plant calculations change materially with pressure basis, reference conditions, efficiencies and operating profile. Explicit assumptions make the result auditable instead of hiding those choices.