At a glance
- At 6 bar, a 1 mm hole loses around 1.2 liters of air per second – around the clock, as long as the network is pressurized.
- The loss grows with the square of the diameter: a 3 mm hole loses nine times as much as a 1 mm hole.
- In many plants, a quarter to a third of the compressed air generated escapes through leaks.
- Lowering network pressure by one bar noticeably cuts energy demand – and every leak loses less.
The leak calculator
Enter how many leaks of each size you suspect or have found. Pressure is entered in bar gauge (1 bar ≈ 14.5 psi). All calculations run in your browser only.
The calculation uses the compressed-air rule of thumb: air loss per hole = 1.2 l/s × (diameter in mm)² × (gauge pressure + 1) ÷ 7. These are guide values for round, sharp-edged openings – real leaks differ, but the order of magnitude is right.
Why compressed air is so expensive
A compressor turns most of the electricity it uses into heat. Depending on the system, only a small fraction of the energy input reaches the tool as useful work. Over a compressor’s lifetime, electricity therefore accounts for by far the largest share of total cost – far more than purchase and maintenance.
Leaks are the silent consumer: they keep running during breaks, at night and on weekends, as long as the network is pressurized. And they grow, because couplings wear and hoses age.
Rules of thumb at 6 bar
Assuming 6 kW per m³/min, 4,000 hours under pressure and €0.20 per kWh:
| Hole | Air loss | Power | Cost per year |
|---|---|---|---|
| 1 mm | 1.2 l/s | 0.4 kW | ≈ €350 |
| 2 mm | 4.8 l/s | 1.7 kW | ≈ €1,400 |
| 3 mm | 10.8 l/s | 3.9 kW | ≈ €3,100 |
| 5 mm | 30 l/s | 10.8 kW | ≈ €8,600 |
So a 3 mm hole – about the size of a failed hose clamp – costs roughly as much a year as the lease payments on a small company car. And it’s rarely just one.
Measuring leaks – three methods
1. Load-time test over the weekend
Switch off all consumers, keep the network pressurized and, for one hour, record the periods in which the compressor runs on load. Then: leakage = compressor delivery × load time ÷ total time. If a 6 m³/min compressor runs on load for 15 minutes in one hour, the network is losing around 1.5 m³/min.
2. Receiver pressure-drop test
Bring the network and receiver up to pressure, switch off the compressor and time how long the pressure takes to fall by one or two bar: leakage = volume of receiver and network × pressure drop ÷ time (volume in m³, pressure in bar and time in minutes gives m³/min). The network volume is the unknown – estimate it from pipe length and diameter.
3. Ultrasonic leak detection
Escaping air produces ultrasound, which a detector makes audible even amid the noise of the shop floor. That lets you pinpoint individual leaks – tag each one and fix them in order of size.
Where leaks occur
- Quick couplings and push-in fittings – the most common spot of all
- Hoses, hose clamps and coiled hoses at workstations
- Service units, filters, pressure regulators and lubricators
- Condensate drains that stick open
- Threads, flanges and valves on machines
Staying leak-tight for good
- Run a leak survey once a year – leaks come back when no one is listening.
- Lower the pressure wherever the consumers allow it: every leak loses less, and the compressor needs less energy.
- Shut off the supply at night and on weekends where nothing is running.
- Measure, don’t guess: a compressed-air meter at the network outlet shows the base consumption during breaks – if it rises, there is a new leak.
How irot helps
The Z 500 compressed-air meter from the Zähler by irot family measures consumption per network or hall and flags rising base consumption before it gets expensive – it is in development, and pilot units are available on request. Evaluating electricity, water, heat and compressed air in one place is on the roadmap as irot Energie.
Assumptions and sources
- Air loss per the rule of thumb for choked flow through round orifices (1 mm, 6 bar ≈ 1.2 l/s), scaled by area and absolute pressure
- Specific power and electricity price are inputs – please use the figures for your system and from your electricity bill
- Measurement methods (load time, receiver pressure drop, ultrasound) follow common practice in compressed-air energy consulting
Guide values, not a measurement. For a reliable assessment of your network, measure the leakage with one of the methods described or with a compressed-air meter.