Tools & measurements

Refrigerant leak checks: a practical field guide

Use more than one clue when finding leaks: oil traces, pressure behaviour, detector response, bubbles, joint quality and service history all matter.

Updated 2026-09-01 · 6 min read · HVAC/R service technicians, contractors, merchants and apprentices

Safety and scope note

This article is educational and does not replace manufacturer instructions, qualified technician judgement, South African regulatory requirements, electrical or refrigerant safety rules, or a site-specific risk assessment.
Never pressurise a system above its rated limits or use unsafe gases for pressure testing.
Do not vent refrigerant intentionally during leak checking or repair.

Start with evidence, not assumptions

Low charge symptoms do not automatically prove a leak at the easiest joint to reach. Look for oil staining, rubbed pipework, corrosion, vibration points, damaged service valves, recent repairs, poor flare work and signs around coils. Ask when the previous top-up happened and how quickly performance dropped again.

A structured leak check helps avoid repeated gas additions. It also gives the customer a clearer decision: repair, monitor, isolate a circuit, replace a coil or quote a larger corrective job.

Identify refrigerant type and system design before selecting tools.
Inspect caps, valve cores, flares, brazed joints, coils, distributors and vibration points.
Use lighting and mirrors where access is difficult.
Document suspected points before disturbing them.

Use the right leak-check method

Electronic detectors, bubble solution, pressure testing and standing pressure checks all have a place. Detector sensitivity, sensor condition, wind, humidity, refrigerant type and access can change results. Bubble solution is useful for confirming accessible joints, while pressure testing can reveal whether the whole circuit is sound after repair.

Follow safe practice for the refrigerant and equipment. Recover refrigerant where required, use an appropriate test gas and pressure, and never exceed rated component pressures.

Calibrate or check leak detectors according to the tool instructions.
Avoid testing in strong airflow that carries refrigerant away from the sensor.
Use bubble solution generously on accessible suspect joints.
After repair, pressure-test and evacuate correctly before charging.

Close the loop after the repair

A leak repair is not finished when the hiss stops. Tighten service caps correctly, replace damaged cores or caps, clean residue where appropriate, weigh in charge, record work done and recheck system operation under load. If the coil is leaking in multiple places, be honest about repair reliability.

Good documentation supports future technicians and protects the business if the same site calls back later. Include refrigerant type, recovered or added amount, pressure-test result, vacuum result and final running readings.

Quick field checklist

Look for oil, corrosion, vibration rubs, loose caps and poor joint workmanship.
Select a method suitable for the refrigerant, location and access.
Confirm suspicious points instead of relying on one detector pass.
Pressure-test, evacuate and recharge according to the repair procedure.
Record leak location, method, readings and refrigerant quantity.

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