Fixing refrigerant leaks is a tedious but important task. The following tips can help prevent leaks and speed their repair:

• Use rubber-gasketed brass caps for all service port connections and keep them wrench-tight (rather than just hand-tight). Have plenty of spares on hand—like the valve caps on your car tires, they have a way of wandering off. Replace these gaskets (or the complete caps) periodically, because they can become dry and cracked.
• Enforce a standard of cleanliness for all refrigerant lines. Keep the copper pipes wiped down with a clean rag. Refrigerant leaks also leak oil, and it is easier to find oil on clean pipes.
• Look for leaks first on flanged and screw fittings, rather than on soldered joints.
• Minimize the number of times that refrigerant gauges must be connected to the service ports—each time this happens, it bleeds a bit of refrigerant from the system.
• Repair a leaking coil only once and mark it with paint or chalk. The next time it leaks, replace the coil completely.
• Repairing refrigerant leaks requires several steps, including refrigerant recovery, nitrogen charging, inspection with a leak detector, brazing or otherwise fixing the leak, vacuum drying, and recharging. Fixing a refrigerant leak can cost from US$250 to as much as $1,000 if components such as the evaporator coil must be replaced.