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Why Central Heating and Cooling Systems Leak Water

water leaking through ceiling

Once the weather heats up, we get calls about a variety of AC-related issues, but one of the most urgent is this: “My air conditioner is leaking into my home!”

A leaking air conditioner is a problem that can happen to just about anyone, but the good news is that it’s also preventable. Below we’ll explain why this problem occurs and what you can do to avoid it.


Have you ever noticed that your home feels both cooler and less humid after your AC has been running? This is because air conditioners extract moisture from your indoor air, dehumidifying it. That moisture turns into water (or condensate) that drips down your indoor AC unit’s coil and collects in a drain pan.

All that water collecting in the drain pan leaves your home to the great outdoors through a pipe. This pipe is called the condensate drain line, and it’s typically made of PVC and no more than one inch in diameter.


Depending on your system’s efficiency, it can draw out 20 to 50 gallons of moisture from the air on a hot day. Without a clean, clear drain line and a properly functioning drain pan, you can run into problems really quickly.

These are the three most common reasons why HVAC systems leak water:

Cracked Drain Pan

Because drain pans are made of metal, they’re prone to rust as they age. In fact, it’s common to need at least one drain pan replacement throughout your system’s lifespan. If your drain pan becomes excessively rusty, holes might start forming in the bottom, or it might become brittle enough to crack. This will allow the water to trickle out and start leaking into your home.

Clogged Drain Line

Dust, dirt, mold, and other types of debris can easily clog your home’s narrow drain line. When this happens, water either can’t leave your home fast enough or can’t leave at all. This results in water backing up into the drain pan. From there, it can start to flood into your home and HVAC system because it has no way to drain.

Frozen Coils

Ice can start forming on your indoor AC unit’s coil if the coil is dirty, if the refrigerant levels are too low, or if there’s too little airflow through the system. A frozen coil is bad news for multiple reasons and could be the death of your compressor. Additionally, if the ice melts quickly, all that water can overwhelm your drain pan and cause it to flood, especially if the drain line is already partially clogged. These are issues we tend to see in systems that haven’t had maintenance in a long time.


No one wants to deal with a homeowners insurance claim to repair water damage. Instead of repairing damage from a leaking AC, here’s how to prevent the issue in the first place.

Keep Up With Maintenance

Getting your HVAC system inspected and maintained annually is the best way to prevent a drain pan or drain line problem. Make sure that the technician clears debris from the drain line and checks for any sign that your drain pan might need a replacement.

Consider Updating Your Drain Line

Newer air conditioning systems produce a considerable amount of water compared to their predecessors from even just ten years ago. A new, high-efficiency system could produce double or triple the condensation of your old system. That being said, a drain line that worked for your old system might not be adequate for your new one. If you’re not sure, consult an HVAC & plumbing company for help determining if a drain line update is needed.

Install a Float Switch

An HVAC technician can install a device called a float switch in your air conditioner’s drain pan. When the pan’s water level rises to a certain amount, the switch will shut off your air conditioner. This prevents the unit from making more condensation and stops a flood before it happens.

At 1st Home & Commercial Services, we will always put your comfort first. Call us now for heating and AC services in Austin at (512) 957-2992 or use our online form.

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