Finding and fixing compressed air leaks

What leaks cost

Compressed Air Systems Fact Sheet #7 (May 2026, Rev. 1), part of the Improving Compressed Air System Performance sourcebook series, says a typical plant that has not been well maintained will likely have a leak rate equal to 20% of total compressed air production capacity, while proactive leak detection and repair can reduce leaks to less than 10% of compressor output. Leaks also drop system pressure, which can make air tools less efficient; force equipment to cycle more often, shortening the life of almost all system equipment; add maintenance and unscheduled downtime; and can lead to adding unnecessary compressor capacity.

Where leaks occur

The fact sheet names the most common problem areas:

• Couplings, hoses, tubes and fittings
• Pressure regulators
• Open condensate traps and shut-off valves
• Pipe joints, disconnects and thread sealants

Estimating the leak rate

For compressors with start/stop controls, the fact sheet starts the compressor with all air-operated end-use equipment turned off and times the load and unload cycles that the leaks cause. Leakage (%) = (T × 100) / (T + t), where T is the on-load time and t the off-load time, in minutes. It should be less than 10% in a well-maintained system; poorly maintained systems can lose as much as 20 to 30% of air capacity and power.

With other control strategies, leakage can be estimated with a pressure gauge downstream of the receiver and an estimate of total system volume, timing the drop from normal operating pressure to about one-half of it. The fact sheet recommends carrying out these tests quarterly as part of a regular leak detection and repair program.

Detecting leaks

According to the fact sheet, "the best way to detect leaks" is an ultrasonic acoustic detector, which recognises the high frequency hissing of air leaks; soapy water applied with a paint brush is simpler and reliable but can be time consuming. The 2016 sourcebook notes that ultrasonic detectors are generally unaffected by background noise in the audible range, can find mid- to large-sized leaks and can test while equipment is running.

Fixing leaks and keeping them fixed

Leaks occur most often at joints and connections. A fix can be as simple as tightening a connection or as complex as replacing couplings, fittings, pipe sections, hoses, joints, drains and traps, and in many cases the cause is bad or improperly applied thread sealant. Equipment no longer in use should be isolated with a valve. Reduced system pressure results in reduced leakage rates, and once leaks are repaired the compressor control system should be re-evaluated to realise the savings. The fact sheet lists the parts of a leak prevention program as identification (including tagging), tracking, repair, verification and employee involvement.

For a review of the whole system, ISO 11011:2013 sets requirements for conducting and reporting a compressed air system assessment, from energy inputs to work done, including the forms of compressed air waste on the demand side; iso.org shows it at stage 90.92, to be revised. For hospital pipelines, see how to detect leaks in a medical gas network.