How is a refrigerant leak found and fixed?

A refrigerant leak is fixed in a set order: a certified technician finds the leak, recovers the refrigerant still in the system, repairs the damaged tubing or fitting or replaces the leaking coil, proves the repair with a nitrogen pressure test, pulls a vacuum, and recharges the system to the manufacturer's specified amount. Every part of that work happens inside the sealed refrigerant circuit, so it is a job for a licensed HVAC pro, not a homeowner.

Why the leak has to be found

A central air conditioner or heat pump does not use up refrigerant. If the charge is low, the system either has a leak or was charged incorrectly when it was installed.^[4][1] That is why a recharge on its own does not fix anything. The EPA asks homeowners to have technicians locate and repair leaks instead of "topping off" a leaking system, which also cuts future service calls and repair costs.^[6]

Leaks are not inevitable. Major leaks rarely develop in properly installed and regularly maintained units.^[6] When one does appear, the job is to find where and why. If you are not sure the system is low at all, start with how to tell if your AC is low on refrigerant.

Where leaks usually start

Knowing the common spots explains why a technician searches where they do. Chemicals in household air, such as hairspray, cleaning supplies and air fresheners, can react with copper coils and eat tiny pinholes in them, a process called formicary corrosion.^[1] Vibration can rub a copper line against another part until it wears through, joints that were poorly soldered at installation can weaken over time, and lawn equipment or falling debris can damage the lines at the outdoor unit.^[1]

On a ductless mini-split, the technician also checks the flare fittings where the refrigerant lines connect the outdoor unit to the indoor units, and in some cases tightening a fitting is the whole repair.^[4]

Finding the leak

Technicians use three main tools, often more than one on the same call. An electronic leak detector, often called a sniffer, senses refrigerant in the air near a leak.^[2][1] UV dye added to the system circulates with the refrigerant, escapes at the leak and glows under an ultraviolet light.^[2] A soap bubble solution brushed or sprayed on the copper lines and joints shows the exact pinhole or crack.^[1]

Small leaks are hard to find with bubbles alone,^[3] and pinpointing a leak can take time,^[4] especially when it sits inside an indoor coil behind panels. You can save some of that time by telling the technician what you have noticed: when cooling dropped off, any ice, and whether you have seen an oily stain or residue at a fitting or valve, or a hissing sound near the refrigerant lines.^[3]

Recovering the refrigerant

Before the circuit is opened, the technician recovers the remaining refrigerant with a recovery machine into a certified recovery cylinder.^[1] Under Section 608 of the Clean Air Act, EPA regulations prohibit intentionally venting refrigerant while servicing, repairing or disposing of air-conditioning equipment.^[7]

On equipment holding more than five pounds of refrigerant, technicians must evacuate it to set vacuum levels when they open it for service or repair.^[8] When a leak keeps them from reaching those levels, they must isolate the leaking parts where possible, evacuate the parts that do not leak to the normal level, and take the leaking parts as low as they can go without contaminating the refrigerant, never above 0 psig.^[8] Recovered refrigerant can go back into the same system or another system owned by the same person; if it changes hands, it must be reclaimed by an EPA-certified reclaimer.^[8]

Repairing the leak

The repair depends on where the leak is and how much of the part is damaged. For a leak in copper tubing, the technician usually cuts out the damaged section and brazes a new piece in its place.^[1] When corrosion has spread through an evaporator or condenser coil, the coil itself is replaced.^[1][2]

The refrigerant your system uses shapes the options. Under EPA rules, a homeowner can have a faulty component such as a condensing unit or indoor coil replaced with a similar R-410A component.^[9] After January 1, 2026, a whole new system must use a lower-GWP refrigerant, and replacing the condensing unit and indoor coil together counts as a new system.^[9] For a coil-or-system decision, see whether to replace the whole AC system or just the condenser.

Older systems usually run on R-22. There are no drop-in replacements for R-22 (HCFC-22), so technicians who repair leaks in an R-22 system most often recharge it with HCFC-22.^[6] No new HCFC-22 has been made or imported into the United States since January 1, 2020, but used HCFC-22 cleaned to the same specifications as new remains available.^[6]

Testing, evacuating and recharging

A repair is not finished until it is proven. The technician pressurizes the refrigerant circuit with dry nitrogen and watches for any loss of pressure, using the test pressure and hold time the equipment manufacturer specifies.^[1][2] After the pressure test, the nitrogen is released and a vacuum pump pulls air and moisture out of the circuit.^[1][2]

The system is then charged with the type and amount of refrigerant the manufacturer specifies. The refrigerant is weighed as it goes in, and the technician checks superheat and subcooling to confirm the system is running as designed.^[1][2] A good invoice says where the leak was, what was repaired, how the repair was tested and how many pounds of which refrigerant went back in.

What not to put in the system

Over-the-counter leak sealants, often sold as "stop leak," are not a substitute for finding and repairing the leak, and manufacturers generally do not recommend them because they can clog the expansion valve and damage the compressor over time.^[2][1] Homeowners also cannot legally buy or charge refrigerant for a home system; why a homeowner cannot recharge their own AC explains the rules.

While you wait for the repair

Running the air conditioner with a refrigerant leak can damage the system further, so shut it off until the repair is made.^[3] If you see ice on the indoor coil or the refrigerant lines, switch the thermostat from Cool to Off and do not chip at the ice, which can damage the coil.^[5] A fan or a portable unit can carry a room for a day or two.

When to call a licensed pro

Call as soon as you suspect a leak: warm air, ice, hissing, or a system that runs all afternoon without reaching the setpoint. Ask whether the company's technicians are Section 608-certified; you can ask a technician to show you the certification card.^[6]

In Virginia, no individual may work, or offer to work, as a tradesman in heating, ventilation and air conditioning for the public for pay without a licence, unless working under the supervision of a tradesman licensed in that specialty.^[10][11] Check the business on DPOR's License Lookup^[12] before work starts. For what the repair is likely to cost, read what fixing a refrigerant leak costs in Virginia.

Getting it fixed

Loclis lists DPOR-licensed HVAC businesses with their licence number and class. Find HVAC businesses in Blacksburg or another town, see refrigerant leak repairs, or browse more HVAC repair answers.

If you think your system is leaking refrigerant, describe what it is doing once and licensed local HVAC businesses quote the repair.