Why Is My AC Leaking Water?

5 Common Causes with Simple Solutions

By James K. Kim

It seems every summer is hotter than the previous one, and your home’s central air conditioning system is probably working overtime to keep up.

Many homeowners have experienced the unpleasant shock of seeing a soaked ceiling or floor due to water dripping out of their AC unit.

While this is never a pleasant sight, the good news is there is no need to panic as these AC water issues are usually fixable.

However, it’s important first to understand the root cause of why the air conditioning is leaking water to begin with to find the right solution.

Why Is Water Forming in My Air Conditioning System?

Most of today’s central air conditioning systems will usually have both an indoor unit (e.g. an air handler, furnace with an attached coil, a ductless wall-mounted indoor evaporator, etc.) connected to an outdoor unit, such as a condenser or heat pump.

The indoor unit’s evaporator coil is what cools the warm air as it blows over it to help maintain a comfortable indoor temperature.

As this warm air blows over the coil, condensation forms. This is similar to the water droplets forming on the sides of a glass of ice water.

Within the indoor unit, a condensate drain pan with a connected condensate drain line leading out of the home prevents this water from leaking into your home.

But unfortunately, this water could still find a way to leak out. Here are a few reasons why this could be happening and how to solve the issue.

1. The drain pan is aged

During the cooling process, the indoor air conditioning unit absorbs heat and draws moisture from the home’s hot air. This heat is absorbed by the refrigerant in the evaporator coil and the resulting moisture trickles down the coil and collects in the drain pan.

However, as it ages, this drain pan can start to rust and develop cracks. As a result, the water collecting in it can start to leak into your home.

Your trusted HVAC service provider of choice should be able to diagnose this issue and offer you a replacement of the system’s drain pan.

2. The condensate drain line is clogged or disconnected

The drain pan mentioned above has a condensate drain line that allows the water to exit your home. However, over time this condensate drain line can get clogged due to collected dust, mold, and other grimy debris that collects over time.

This clog blocks water from flowing out, leading to the drain pan filling up and spilling over onto the floor (and possibly leaking through the ceiling if the indoor unit is located in the attic).

An HVAC service technician can solve this issue by unclogging and cleaning your condensate drain line, allowing water to flow freely and safely drain the water away.

If the condensate drain line has become disconnected, you will also see water leakage. This is also a relatively straightforward repair that a professional HVAC service tech can easily address.

3. The evaporator coil is frozen

Another common reason why your AC is leaking water might be a frozen coil.

Since the evaporator coil contains refrigerant, it becomes extremely cold.

If ice forms on the coil, it will lead to the air conditioning losing its cooling ability and will start to overheat. As this ice melts from the heat, the water will flood the drain pan and leak out onto the floor.

A frozen coil is a major HVAC issue that should not be taken lightly, as subsequent damage may have occurred as well when it froze. If you see ice forming on your evaporator coil, it’s best to reach out to a trained HVAC technician who knows how to safely handle refrigerant to prevent its toxic spread into the environment.

4. The AC system is low on refrigerant

Another reason why the coil can freeze over is due to low refrigerant levels caused by a leak somewhere in the system.

That’s because the pressure inside the air conditioning system is decreased as the refrigerant volume decreases. Again, this leads to a frozen, iced-over coil and subsequent leak.

An HVAC service technician has special tools that can measure the refrigerant levels in your air conditioning system if a refrigerant leak is suspected due to water leakage or the home not cooling like it used to.

The good news is a leak that is detected early could be remedied relatively quickly and without incurring a massive expense, or a total system failure requiring a complete replacement.

The best way to prevent issues from low refrigerant in the air conditioning system is by having regular maintenance by an HVAC service technician.

A seasonal maintenance visit by an HVAC tech will include a system operation inspection to clean and calibrate critical mechanical components to ensure your unit is running in tip-top shape and ready to cool.

5. The air filter is dirty

Another possible reason why ice forms on the evaporator coil leading to leaking water is a lack of airflow through the AC system. A potential cause could be a clogged air filter filled with dust and debris.

A clogged filter will make your system struggle to draw air through it, leading to a lack of warm air flow over the cold evaporator coil, resulting in frost and icing. A buildup of dust or grime on the evaporator coil could also cause ice formation. Depending on the air quality within your home (e.g. pets, allergy sensitivities, smoking, etc.), AC filters should be changed every 30-60 days.

Some AC systems can get damaged or completely worn out if a filter is dirty or clogged. That’s because a dirty filter “chokes” the HVAC system and impedes airflow over the evaporator coil. Without the airflow, the coil gets frozen, ice forms over it, then eventually melts and leaks out.

Conclusion

Most of these reasons why an air conditioning system is leaking water can usually be prevented during a regular seasonal AC maintenance visit by an experienced and knowledgeable HVAC service technician.

A tech can examine the major mechanical components and known potential leak causes to get in front of potential future water leaks, operational efficiency barriers, and system breakdowns.

Be sure to work with a reputable and reliable HVAC company to provide routine maintenance on your heating and air conditioning systems to ensure your home is comfortable year-round and your energy costs are low.