Many air conditioners die not from a mechanical issue but a lack of refrigerant.
This can happen at any time during its life cycle. And yes, we have seen air conditioners leak refrigerant from the factory! But,under normal use and expert installation, an air conditioner should not leak its charge. An air conditioner is fully sealed- hermetically sealed (for the nerds here 🙂) and will maintain its charge from the factory without any issues.
But, sometimes as fate would have it, an air conditioner will leak refrigerant- but why? Let’s discuss that here. I have been in the field for over 20 years and seen a lot of different systems and in a lot of different applications. Refrigerant leaks stem from a wide range of problems – but the 3 main faults are installation, manufacture, and/or design. It takes a lot of skill to assess why the leak happened in order to prevent it from happening again. Almost any tech nowadays can locate a leak, but many younger techs are unaware of how to design a new system for a leak to not happen again.
Let’s first make sure we get some facts lined up about air conditioner systems. There are 3 main components to an air conditioner- the indoor unit,the outdoor unit, and the refrigerant lines that connect both the outdoor and indoor units. Pretty basic breakdown because yeah there certainly is more to it than that, but this breaks it down to their simplest components. From here we can begin examining each part and evaluate where leaks develop and why they happen.

We will cover: where common refrigerant system leaks develop, should I fix my system or replace it, how can I prevent future leaks?
Let’s start with the indoor system, or evaporator coil.
The way an evaporator coil works essentially is to absorb heat-transfer that heat to the refrigerant traveling in the coil lines and then reject that heat outside. That’s why when you put your hand over the top of the outdoor unit it’s hot. (unless the system isn’t working) As this evaporator coil absorbs heat and transfers it, condensation naturally occurs. In fact, a main part of air conditioning is managing moisture, or removing it. Moist air holds more heat! Condensation with aluminum and copper create formicary rust or formicary corrosion. This affects copper and copper based alloys.
I will say that based on experience, the older is better adage doesn’t prove true with this. Most of the coils manufactured when R22 was in service were copper and aluminum based.
These rust “spots” or areas will develop into small leaks. “Pinhole leaks” is what we refer to them in the hvac industry. Now, not usually a problem, at first.
An air conditioner can continue to operate and cool the house for many seasons even with a pinhole leak. A pinhole leak might take years for the a/c system to start showing signs of failure. In fact, most of the time, contractors never even locate the leaks- more on this a little further in the article.
When the system gets low enough on it’s refrigerant charge,the system will typically display some common issues- ice build up or development in the evap coils and refrigerant lines. Reduced performance in cooling mode- it will seem like the air conditioner takes forever to cool the house down. And in some cases, the compressor outside will begin operating louder than normal because there is less oil present for motor lubrication. In all these instances though, it is not sudden. These issues happen out of sight out of mind.
A technician will come out and diagnose the problem- finding low charge and then simply recharge the unit. To locate the leak, means digging in a bit deeper and taking the thorough time to evaluate. When one pinhole leak is found in the evap coil, there can often be more present and more difficult to assess.


I like to take note of all known issues and then schedule a re-visit for following season to assess the “rate of leak”. Remember, some leaks are so small that they may lose 10% of its charge over the course of 5 seasons. In any instance though, the rust and pinhole leaks will not fix themselves- it will continue to develop worse and worse.
At that instance, it’s time to evaluate the best course of action-replacement or continued repairs?
If your system is older and utilizes R22, that can be very expensive. And even some contractors refuse to charge older systems due to liability or product availability. Most home air conditioner systems hold 4-8 pounds of refrigerant. And at $100-$200 per pound, that repair bill can add up pretty quickly.
Remember that copper and aluminum reference from earlier? Why don’t the air conditioner manufacturers just make coils that will last? Well, great question but not as easily managed. Copper is a better heat transfer media than aluminum or alloy. And copper can be welded a lot easier than aluminum- important for field work. There are several brands that do now utilize a single material in the evaporator coil manufacturing process. In our experience, evap coils manufactured with aluminum last a lot longer with fewer leaks than their copper counterparts.
Aluminum has it’s own set of issues but it definitely outshines in the leak department.
Pinhole leaks are the most common form of refrigerant leak failures. I’d say they account for approximately 80% of all recordable refrigerant leaks in systems.
Can this be avoided? Not really is what I tell my homeowners. When replacing your system, you can ask for a brand that has an all aluminum evap coil.
One other note here on condensation and the indoor evap coil. Too much airflow or too little airflow has been a growing concern the last decade. Airflow design has always been a consideration but systems used to be more “robust” or less sensitive. Many modern and efficient air conditioning systems today are very sensitive to airflow. Too little airflow – think a restricted or dirty air filter, lack of proper duct design, closed off vents- and the condensation production goes up. Too much airflow and the system doesn’t remove as much humidity making the indoor climate more muggy or clammy.
Airflow design also has a lot to do with the size (tonnage) of the system. Many homes today with systems replaced in the last 10-20 years are way oversized because a lot of homeowners, and contractors alike, ascribed to the bigger is better methodology.
And just a quick note on brands and the different manufactures- all systems will have the same issues if theyre installed poorly or incorrectly. We see a lot of lower tier brands that are 20 plus years old and still running very well. On the flip side, we have worked on some higher tier air conditioning systems that are barely 5 years old. According to ASHRAE, airflow and duct design is overlooked on more than 80% of installed systems today.
Main point here is to communicate focus on installation methods over specific brands.
Now, the outdoor portion, or the condenser will develop leaks as well, let’s examine a few of those problematic areas. When a leak develops outside, this is often visible to the eye because the refrigerant is oil at this stage of the air conditioning process. And it acts just like oil in your driveway. It will collect dirt and dust and be very visible. Most outdoor leaks show up like this.
But, what else lives outside in the yard? Our beloved pets! What’s that have to do with the air conditioner? Well, many dogs LOVE to use the air conditioner as their pee post! That’s right. For whatever reason dogs are attracted to the thing that brings our homes a lot of comfort during the hot summer months.

A dog’s pee is highly corrosive in nature- ever see those unsightly yellow spots in lawns? Likely from a dog peeing. Over time- in some cases this rate is fast and in other cases this rate is very slow- the condenser coil will break down, the copper will break down and eventually develop a refrigerant leak.
These areas are a lot easier to spot since they’re outside but how many of us actually check our air conditioner condenser coil on any regular basis?! Great reminder for the importance of routine maintenance!
Can this be avoided? Unlikely. Unless we give ol’ Fido the kick to the curb. But he’s been around the family since little Billy’s 5th Christmas and now in every family photo since!
We have seen some success with spraying the coils down with regular distilled vinegar as this repels a dog from the air conditioner but we haven’t found any conclusive evidence to support this claim.
And the last and final area for potential leaks are the lines themselves.
Refrigerant lines can leak from a number of issues but likely is the result of some sort of human damage or human interference. Think a weed whacker clipping a line or a dog chewing through copper- yep, we’ve seen both.
On one home we went to, the copper lines were removed from the home for recycling money! The unit was still there, just upon closer examination we found someone had stolen the lines!
Most cases though involve poor installation methods. Many systems have different sizes of copper line connections and contractors will utilize copper fittings to get from one existing size to a newer lineset size. These connections pose a potential problem for longevity if they weren’t welded correctly.

We use a copper swage tool in these instances. This helps eliminate the number of joint connections throughout the system. THose tools are expensive and many of those tools need to be well cared for causing most contractors to overlook the added expense. One copper fitting typically runs $2 compared to a $600 swage tool.
Refrigerants have been all over the map the last decade or so- new blends and some becoming “phased out” or “extinct”. This has brought up a lot of debate around this particular area of systems leaking. When should you ditch the system because of a leak? Is it age or cost of repair? How will the new one perform better?
The main recommendation I can make here is for routine maintenance. While that won’t be a magic bullet and prevent leaks from happening, you can often get ahead of things before they become much larger issues.
The common repairs for a leaking air conditioner include charging the system, adding in a secondary product called “leak stop”, welding the system to close up the leak, or replacing the leaking components throughout the system. That last option usually means replacing the system but in all cases it’s always worth evaluating if that’s the best route or not.
Leak stop works very similarly to slime in a bike tire. This is best used on small leaks, typically for evaporator coils where small pinhole leaks develop. While it is not a guarantee to stop and prevent leak, it’s a relatively low risk cost to try out before a more costly system overhaul. There is certainly a lot of debate in the industry whether adding leak stop should be done preemptively and even to its effectiveness.
We usually recommend adding leak stop as a last ditch effort before full replacement or replacement of the evaporator coils. If the leak is in the outdoor unit, the recommendation is replacement of the whole system, this is often cheaper, and comes with a parts and labor warranty.
At Gem Heating & Air Conditioning of Boise, Idaho, we believe in providing our customers with options that lead to real solutions. In order to provide real solutions we have to be thorough in our diagnosis and evaluations. We go the extra mile. Why? Because even though times change, good ol’ fashioned service hasn’t. Reach out if you think yout system is low or has a leak or if you think you need a second opinion on something. Contact us for an honest assessment of your HVAC system today!
