Have you noticed that your AC system is leaking water inside your house or there is water dripping out of the AC condenser outside? Both of these issues are fairly common and are related to condensation. While water dripping out of the unit outside is usually nothing to worry about, water leaking inside is a sign that your AC has some type of issue. In this article, we’ll explain what can cause an AC to leak water so that you know what to look for and what to do when this happens.

Why AC Systems Create Condensation

During normal operation, condensation forms in the indoor part of an AC system on the evaporator coil. This moisture accumulates when warm air in your home flows over the coil, similar to water droplets forming on a glass of cold water. It’s a byproduct of the system capturing heat energy from the air with cooled refrigerant. On a hot day, your cooling system can pull up to 20 gallons of water out of your home’s air. The process is beneficial because many central air conditioning systems can regulate the humidity in your home without needing to install a separate dehumidifier.

All of the water that forms on the coil is why all ACs have a condensate drain system that captures the water and allows it to drain elsewhere. Many AC systems direct condensation into a floor drain near the indoor air handler, but others are set up so that the water drains outside. The latter setup is most common in homes where the air handler is located in the attic or on the ground floor. In addition, if your air handler is in a basement or crawl space, your cooling system most likely has a condensate pump to overcome gravity so that the water drains outside.

While condensation mostly forms on the evaporator coil inside the home, there are times when you may see some water dripping outside when your cooling system is operating. This happens because the refrigerant in the system releases the heat it pulled out of the house and then again gets cooled before being pumped back inside. This process can result in some condensation forming on the copper line that carries the cold coolant back inside, leading to a small amount of water dripping off. While usually not a significant issue, ensuring that the return refrigerant line is well insulated will eliminate condensation and may improve the efficiency of your system.

What Causes an AC System to Leak Water Inside a Home?

If you notice that water is leaking out of the air handler inside your house or there is water pooled up below, it often indicates that the system isn’t draining properly. An AC condensate drain system consists of a drain pan that is located directly underneath the evaporator coil. The pan is connected to a condensate line that carries the water out of the air handler so that it drains away elsewhere.

It’s fairly common for the drain pan or one of the condensate lines to get clogged. This blockage typically happens as a result of debris or algae building up to the point where the system clogs. All of the water obviously won’t be able to drain away properly if the condensate system is blocked. Unfortunately, the water will continually collect in the drain pan until it becomes so full that it begins to overflow, and water starts leaking out of the air handler. Clearing a clog in the drain pan’s drain hole is usually fairly easy, but you’ll typically need the help of an AC technician if there is a clog somewhere in one of the drain lines.

The drain pan itself can also sometimes develop a small hole or crack that allows water to leak out. This is especially common for AC systems with a metal drain pan since the metal can rust and degrade over time. It’s often possible for an HVAC professional to repair or replace a drain pan. However, some AC systems have a drain pan that is welded onto the base of the evaporator coil. In this case, the drain pan can’t be removed to replace it, which means the only option is to replace the entire evaporator coil assembly.

Another potential reason your AC is leaking is that one of the drain lines is cracked or there is a loose connection where two pieces of pipe meet. You can easily check for this by feeling along the line to see where the water is coming from. Additionally, if your cooling system has a condensate pump, it can become clogged or malfunction due to wear and tear. An HVAC technician can replace damaged drain lines and clean out or replace drainage pumps.

If your condensate drain system is in good shape and draining properly, a water leak in your home could result from your cooling system freezing up. When the system shuts off, ice that has formed on the evaporator coils melts. This means that water may collect in the drain pan faster than it can drain away, leading to the pan quickly overflowing.

Freezing Versus Drain System Issues

Knowing whether your AC is leaking due to an issue with the condensate drain system or because the evaporator coil is frozen is fairly easy. The reason is that you’ll quickly end up with hot air blowing out of all the vents in your house any time your AC freezes up. Any time you suspect your AC is frozen, it’s important that you immediately shut it off. This is because severe damage can occur to the compressor if you leave your AC running when the evaporator coil is frozen.

What Can Cause an AC to Freeze?

An AC system can freeze up for a few different reasons. The most common reason is that the system isn’t receiving sufficient airflow either because the air filter is too dirty or the blower isn’t working effectively. This is why it’s a good idea to replace the air filter if your AC freezes up since sometimes that’s all it takes to get it working properly again.

A buildup of dust on the evaporator coil can also lead to it freezing up, which is something you can usually prevent with annual maintenance. The issue in this situation is that the dust effectively insulates the coil, which limits the ability of the refrigerant to capture heat. If the refrigerant isn’t capturing as much heat as it should, it often leads to the coil getting cold enough that the condensation on it begins to freeze.

Contact the Professionals

If your AC is leaking or freezing, Markool Heating & Cooling is always ready to help. We offer expert AC repairs and maintenance, and we also specialize in cooling system installation and a full range of heating and plumbing services. Contact us today for more information or to schedule a service call in the Frederick area.

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