How we fixed it: We replaced the entire distribution system with 40mm modular aluminium pipe for the main trunk line, stepping down to 25mm at the branch points feeding each bay. The main line was laid as a ring (loop) system rather than a dead-end run — meaning air can reach any bay from two directions, halving the effective flow distance and dramatically reducing pressure drop. All sharp 90° elbows were replaced with long-radius bends. Drip legs with automatic drain valves were installed at every low point and at each bay takeoff.
The result was immediate: pressure at the spray gun stabilised at 6.2 bar under full shop load, with no variation during peak demand. The painters noticed the difference within the first hour of use.
The lesson: Never reuse old pipework when upgrading to a higher-capacity compressor. The pipe sizing must match the new flow rate, not the old one. As a practical guide, keep air velocity in main distribution lines below 6–8 m/s, and always use a ring system in any facility longer than 20 metres. Every unnecessary elbow and every pipe diameter reduction costs you pressure — and pressure costs you energy.
| Pipe Diameter | Max Recommended Flow (approx.) |
|---|---|
| 19 mm (3/4″) | up to 15 CFM |
| 25 mm (1″) | up to 30 CFM |
| 32 mm (1¼”) | up to 50 CFM |
| 40 mm (1½”) | up to 75 CFM |
| 50 mm (2″) | up to 120 CFM |
