3 Leak Detection and Repair

Purpose of leak repair

A refrigerant leak can reduce system charge, impair performance, and expose people to hazards. Effective service requires locating the leak, choosing a repair that restores the pressure boundary, and verifying the result—not merely confirming that pressure is falling.

Prepare safely

Before testing or opening a system, identify the refrigerant, appliance type, design pressures, and any special hazards. Check the equipment nameplate and the manufacturer's service instructions. High- and very-high-pressure appliances can store substantial energy, so gauges, hoses, fittings, and tools must be rated for the pressure and refrigerant.

Follow applicable training, certification, site procedures, and regulations. In the United States, do not intentionally vent refrigerant during service; recover it using appropriate equipment. Provide suitable ventilation because refrigerant vapor can displace oxygen, and some refrigerants are flammable. For flammable refrigerants, follow equipment-specific precautions for ignition sources, ventilation, leak detection, and electrical equipment.

Wear appropriate eye and hand protection, and avoid contact with liquid refrigerant, which can cause frostbite. If a leak creates a suspected hazardous atmosphere, leave the area and follow emergency procedures rather than continuing to troubleshoot.

Before brazing or other hot work, recover refrigerant from the affected section, isolate it, and follow required hot-work and fire-safety procedures. Use a controlled nitrogen purge when the approved brazing procedure calls for one.

Locate the leak

Inspect the entire accessible refrigerant circuit. Check service ports and caps, valve stems, flare or threaded joints, brazed joints, vibration points, coils, headers, receiver connections, and areas with oil residue, corrosion, or mechanical damage. Oil staining can indicate a leak, but its absence does not prove tightness.

Choose a method suited to the refrigerant, likely leak size, and access:

• Electronic refrigerant detector: Use a detector suitable for the refrigerant and maintain and operate it according to its instructions. Check its function before use. Move the probe slowly near likely leak points, avoid drafts that can disperse refrigerant, and recheck a suspected location from more than one direction.

• Bubble solution: Apply an approved leak-detection solution suitable for refrigeration service to an accessible joint or surface, then watch for growing bubbles. Clean the solution off afterward if required.

• Ultrasonic detection: This can be useful where escaping gas produces detectable ultrasound, including some settings where refrigerant concentration is low. Reduce background noise and, when practical, confirm findings with another suitable method.

• Ultraviolet dye: Use dye only when it is compatible with the system and permitted by the manufacturer. It can help identify some leaks, but is not suitable for every appliance or leak location.

• Pressure or vacuum testing: A pressure-hold or vacuum-rise test can show that a system or isolated section may be leaking, but it does not locate the leak. Pair it with a method that identifies the leak's position.

If the leak is not found, divide the system into sections using approved isolation points and test each section in turn. Record the locations inspected and methods used. EPA guidance distinguishes a leak inspection that locates leaks from tests that only show whether pressure or vacuum changes.

Choose a durable repair

Base the repair on the leak location, component condition, accessibility, and manufacturer's instructions. Tightening a connection is appropriate only when the joint design and procedure allow it; over-tightening can damage threads, flare faces, or seals. Replace defective seals or service-port cores with compatible parts, and install or replace caps as specified.

For damaged tubing, coils, or other pressure-containing components, use an approved repair method and qualified personnel. Depending on the component and damage, the appropriate choice may be a permitted brazed repair, replacement of the affected section, or replacement of the component. Stop-leak additives are not a substitute for locating and correcting the source. If a safe, durable repair is not feasible, follow the owner's and manufacturer's procedures for component replacement or equipment retirement.

Repair and verify

Adapt this sequence to the appliance and the manufacturer's service procedure:

1. Recover and isolate. Recover refrigerant from the section to be opened; do not vent it. Isolate the section where possible and confirm that it is safe to work on before loosening any connection.

2. Make the repair. Use compatible components and approved tools and joining methods. Protect nearby components from heat or mechanical damage. For brazing, follow the specified purge and hot-work precautions.

3. Pressure-test safely. Use dry nitrogen with a suitable regulator and pressure-control equipment. Never use oxygen or compressed air to pressure-test a refrigeration system. Raise pressure in controlled steps, and never exceed the manufacturer's specified test pressure or the allowable limit of the weakest component in the section. Check repaired joints with an appropriate detector or bubble solution. A pressure hold can supplement, but cannot replace, leak-location methods.

4. Correct any failure. If a leak is found, safely release test pressure, repair the defect, and retest the repaired area. Do not tighten or adjust joints while they are pressurized.

5. Evacuate and recharge. After a successful leak test, remove nitrogen as required, evacuate and dehydrate the system using the prescribed procedure, and then charge it with the specified refrigerant and amount. Avoid cross-contamination and use proper recovery and charging practices.

6. Check operation. Return the appliance to normal operation and inspect repaired areas again with a suitable leak-detection method. Confirm stable operation and check for signs of continuing loss.

7. Document the work. Record the leak location, test and repair methods, parts replaced, refrigerant recovered and added, verification results, and any required customer or regulatory information.

Regulatory requirements

Leak-repair obligations depend on the refrigerant, appliance charge, and equipment category; they are not identical for every system. In the United States, EPA Section 608 requirements apply to specified appliances containing ozone-depleting refrigerants. Separate AIM Act requirements that began January 1, 2026 apply to certain appliances containing HFCs or specified substitutes, with defined scope and exceptions. Owners and technicians should consult current EPA regulations and guidance for the appliance being serviced.

• Pressure-decay test

• Refrigerant recovery

• Leak-location method