Guide
How Much Steam Does a Failed Trap Waste?
A single failed-open steam trap can waste more steam than you think. Learn how to estimate steam loss, understand the factors that determine waste, and see real-world examples.
5 min readUpdated July 2026
Factors That Determine Steam Loss
- Orifice size: Larger orifice = more steam lost. A 5mm orifice wastes ~2.8x more steam than a 3mm orifice at the same pressure.
- Steam pressure: Higher pressure = higher steam density = more mass lost per unit of volume flow.
- Operating hours: A trap that operates 24/7 wastes 3.5x more steam than one that operates 8 hours/day.
- Back pressure: Higher condensate return pressure reduces the differential pressure across the trap, reducing steam loss.
Quick Reference Table
Approximate steam loss (kg/hr) for a fully failed-open trap at various pressures and orifice sizes:
| Orifice Size | 3 bar | 7 bar | 10 bar | 15 bar |
|---|---|---|---|---|
| 2 mm | ~2 kg/hr | ~4 kg/hr | ~5 kg/hr | ~7 kg/hr |
| 3 mm | ~5 kg/hr | ~9 kg/hr | ~12 kg/hr | ~16 kg/hr |
| 5 mm | ~13 kg/hr | ~24 kg/hr | ~33 kg/hr | ~44 kg/hr |
| 8 mm | ~33 kg/hr | ~62 kg/hr | ~84 kg/hr | ~113 kg/hr |
Annual Cost Examples
Assuming steam costs $0.02/kg and the plant operates 8,000 hours/year:
| Orifice | Pressure | Steam Loss | Annual Cost |
|---|---|---|---|
| 3 mm | 10 bar | 12 kg/hr | ~$1,920/year |
| 5 mm | 10 bar | 33 kg/hr | ~$5,280/year |
| 8 mm | 10 bar | 84 kg/hr | ~$13,440/year |
| 5 mm | 15 bar | 44 kg/hr | ~$7,040/year |
The multiplier effect
If 15% of your 100 traps are failed open at an average of $4,000/year each, that's $60,000/year in wasted energy. A trap survey and replacement program typically costs $5,000–$10,000 — the payback is less than 2 months.
Hidden Costs of Failed Traps
- Increased boiler fuel consumption — the boiler must produce replacement steam for what's wasted.
- Higher condensate return temperature — wasted steam pressurises the return system.
- Reduced system capacity — wasted steam may cause boiler to operate at maximum output, limiting capacity for process needs.
- Other traps may fail — elevated back pressure in the condensate return system can cause other traps to fail.
- Environmental impact — wasted fuel means unnecessary carbon emissions.
Tip: Track your boiler fuel consumption per tonne of steam produced. A gradual increase over time often indicates an increasing number of failed steam traps.