3 Leak Detection, Repair, and Verification

Purpose and service sequence

A refrigerant leak wastes charge, reduces system performance, and can create safety and environmental hazards. A reliable service sequence is inspect, locate, assess, repair, and verify. Clues that a system is leaking do not prove where the leak is.

Inspect and locate the leak

Begin by visually inspecting accessible tubing, joints, valves, service ports, coils, heat exchangers, and components subject to vibration or corrosion. Oil or residue can indicate a leak, especially on a hermetic system; unusually high superheat may also be a clue. Neither finding alone confirms a leak.

Use a method that identifies the leak location:

• Apply an approved bubble solution to likely leak points and look for growing bubbles.

• Use an electronic refrigerant detector according to its instructions, moving the probe slowly around joints and suspect areas.

• Use ultrasonic or gas-imaging equipment where appropriate, particularly when access or background conditions make other methods difficult.

A pressure-decay test can show that a system is losing pressure, but it does not locate the leak. Pair it with a locating method. When pressure-testing with dry nitrogen, use a regulator and suitable test equipment, and never exceed the appliance’s or component’s rated test pressure. Do not use oxygen or compressed air to pressure-test a refrigerant system.

Assess and perform the repair

Before selecting a repair, confirm the refrigerant, system design, leak location, and extent of damage. Determine whether a fitting can be properly tightened, a serviceable component replaced, or a damaged coil, line, or other part repaired or replaced. Follow the equipment manufacturer’s procedures and applicable codes. The repair must restore the pressure boundary, not merely hide the symptom.

Before opening the system, recover refrigerant as required and follow applicable evacuation requirements. For high- and very-high-pressure appliances, EPA allows a limited exception for certain non-major repairs that are not followed by evacuation to the environment: the appliance must be at $0\ \text{psig}$ before it is opened. Separate rules apply to major repairs and other circumstances.

If a leak prevents the required evacuation, isolate leaking components where possible. Evacuate non-leaking components to the required level, and evacuate the leaking component as far as practicable without exceeding $0\ \text{psig}$. Never vent refrigerant as a shortcut.

Test and verify system integrity

After repair, pressure-test the repaired section using an appropriate method, then evacuate and recharge according to the equipment manufacturer’s specifications. Keep test pressure within the lowest applicable rating of the appliance and its components. A system-level pressure test supports an integrity check but does not replace close inspection of the repaired site.

Verification has two stages:

1. Initial verification: After repair, confirm that the repaired location is leak-free before adding refrigerant back to the appliance or repaired section.

2. Follow-up verification: Recheck after the appliance returns to normal operating conditions, unless professional judgment indicates the test will be more meaningful before then.

Use a suitable locating method at the repaired site; a system pressure check alone may not identify where a leak remains. If a test fails, do not assume the system is ready for service. Reassess the location, correct the repair, and test again.

Record the leak location, detection method, repair performed, test conditions, results, and refrigerant added or recovered as required.

Understand regulatory requirements

Leak-repair duties depend on the refrigerant, charge, appliance type, and applicable rule—not simply on whether an appliance is high-pressure. As of 2026, EPA’s Section 608 leak-repair requirements apply to appliances with at least $50$ pounds of ozone-depleting refrigerant when the applicable leak-rate threshold is exceeded.

A separate EPA rule, effective January 1, 2026, covers certain appliances with at least $15$ pounds of HFC refrigerant or qualifying substitutes. It excludes residential and light-commercial air conditioning and heat pumps. That rule generally requires initial and follow-up verification for each repaired leak, with follow-up timing specified by the rule.

Owners and operators are responsible for applicable compliance duties; technicians should document and communicate their work. Check the current regulations for the appliance and refrigerant involved.