It is completely normal to see a bit of water pooling up underneath or around the AC unit outside your house when it’s running. This is especially true in hotter, more humid places like Atlanta. If you have your thermostat set fairly low whenever it’s especially hot and humid, your AC will have to work extra hard resulting in much more condensation forming and leaking out of the unit. What you shouldn’t see is water leaking out of the air handler where the interior part of your AC system is located as this indicates that the system has some sort of problem. With that in mind, here are the potential reasons why your AC is leaking water and what can be done to overcome each one.

An Overview of the AC Condensation Drain System

Before we look at the specific causes, you’ll need to understand where the water comes from and how your AC system takes care of it. Air conditioning works by using extremely cold refrigerant to capture and remove heat from the air. This refrigerant flows through the AC evaporator coil, and the AC blower works to pull warm air in from your house and force it over this coil. Since heat energy naturally flows from a high-temperature area into any surrounding areas that are colder, much of the heat in the air blowing over the evaporator coil flows into the coil and is absorbed by the refrigerant.

This process also causes much of the moisture in the air to condense into water droplets on the evaporator coil, which is how air conditioning also helps to control indoor humidity. The easiest to think about how this happens is to consider how condensation forms on a cold glass or bottle in hot weather.

In order to capture and remove all of the water that forms, all AC systems have something known as a condensate drain system. The water first drips off of the evaporator coil into a drain pan, which is connected to a series of PVC drain pipes that channel the water either directly outside or into a floor drain. If you ever notice water leaking out of the air handler compartment or pooling up on the floor below, it indicates that all of the water isn’t draining away for one reason or another.

Clogged or Broken Condensate Pipe

One of the most common reasons that water will start to leak out of the air handler is that the drain system is clogged. Dust and debris can sometimes get into the system and eventually cause one of the pipes to clog. More commonly, however, is that the pipe is clogged due to a build-up of mold, algae, and slime, all of which can easily form in the system due to the combination of high temperatures and moisture.

If a drain pipe becomes completely clogged, the water will start to back up to the point where the drain pan can overflow. Even a partial clog can also cause the pan to overflow in times when your home is more humid and your AC runs for long periods without shutting off. In most cases, you will need to have an AC technician unclog the pipe as this usually requires using specialized equipment to suck out the clog.

Depending on the age of your AC system, a clog can also cause the system to automatically shut down and no longer turn on. This is because many newer systems have a safety switch in the drain pan that will trigger and shut the AC off whenever the drain pan becomes too full to prevent it from overflowing. When this happens, the drain pan will then need to be emptied and the safety switch reset before the AC will turn on again.

If water is pooling up on the floor, it could also be that one of the drain pipes is cracked or one of the joints is loose. This is something you can easily check for by visually inspecting the pipes and feeling all along each one for any water. If the pipe is broken or you have a loose joint, you’ll want to have a technician repair or replace it.

Rusty or Damaged Drain Pan

The drain pan itself can also get damaged or start to rust through to where the water starts to leak out. In this case, you’ll need to have a technician either repair or replace the drain pan. However, if the drain pan is metal, you may not be able to replace it as sometimes it is welded directly onto the bottom of the evaporator coil. In this case, your only option will be to have the entire evaporator coil replaced.

Frozen Evaporator Coil

The evaporator coil can occasionally freeze up for several reasons. A dirty air filter is the most common cause, restricting how much warm air the blower can draw. When there isn’t sufficient warm air coming in, the evaporator coil can stay cold enough that the condensation quickly freezes before it can drip into the drain pan. The same can also happen if the blower is malfunctioning and unable to circulate enough air.

The evaporator coil will also freeze frequently if the system has a leak and is low on refrigerant. Low refrigerant levels cause the pressure in the system to decrease, which then leads to the refrigerant becoming much colder. This causes all of the condensation to freeze.

If you leave your AC running when the coil is frozen, more and more ice will build up. As such, it is always important to shut the system off if you suspect the coil is frozen. You’ll usually notice quite quickly as it will cause warm air to start blowing out of your vents. Shutting off the system when frozen is also important as otherwise there is a chance that the compressor motor in the outdoor unit could burn out.

While you should shut the AC itself off at the thermostat, you should switch the fan setting on the thermostat to “On” so that the fan continues to run. This will allow the coil to thaw more quickly as the fan will pull warm air over it to help melt all of the ice. As the coil thaws, the water can sometimes overwhelm the condensate drain system and trigger overflowing. If you ever notice that your AC is leaking when it’s not currently running, there is a good chance that this is exactly what’s happening. The best way to prevent possible leaks and water damage as the evaporator coil thaws is to place towels underneath the drain pan and on the floor around the air handler.

If you have an AC that’s leaking or experiencing any other issues, you can trust the team at Bardi Heating, Cooling & Plumbing for help. We offer professional AC repairs as well as maintenance and installation services, and our team can also take care of all of your heating, indoor air quality, and plumbing needs. We serve customers throughout Norcross and the Atlanta area so contact us today to get the expert AC services you need.

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