Refrigerant Leaks at Startup: Identifying and Preventing Common Issues

Refrigerant leaks are one of those problems that build quietly. Your air conditioner or heat pump won't suddenly stop working, but a small leak can slowly reduce cooling performance and damage internal parts over time. Industry experts say leaks are usually found in one of two spots: older systems, or newly installed ones.

In systems five to ten years old, the leak is almost always at the indoor evaporator coil (the indoor unit that absorbs heat from your home's air). Corrosion, caused by moisture and airborne chemicals from things like flooring, carpet, and paint, slowly eats pinholes into the copper. Newer, tightly sealed homes actually make this worse, because those chemicals can't easily escape and instead get pulled into the system. This kind of leak is hard to prevent, since it's tied to how the coil interacts with your home's air over the years.

Leaks in newer systems usually trace back to installation mistakes, particularly in how copper lines were joined together (a process called brazing, which uses heat and filler metal to seal pipe connections). Skipping steps like flowing nitrogen through the lines to prevent oxidation, not cleaning the copper before joining it, or not heating it properly can all leave a weak joint that eventually fails. One expert noted that a thorough pressure test with nitrogen gas right after installation catches most of these problems before they ever become a service call. If you're getting new equipment installed or major components replaced, it's worth knowing that this kind of testing exists and is meant to catch leaks before they show up as a slow loss of cooling down the road.