Window AC Unit Leaking Water Inside.

Window AC Unit Leaking Water Inside? Here’s How to Fix It.

If you observe water dripping from your window air conditioning unit, it’s a clear indication of a problem that requires prompt attention. Window AC Unit Leaking Water Inside can result in water damage, mold growth, and various other concerns. In this post, we will explore the typical reasons behind window AC leaks and provide solutions for addressing them.

At a glance: Window AC Unit Leaking Water Inside due to Clogged drain,Improper installation,Dirty air filters,Low refrigerant levels,Malfunctioning condensate pump,Leakage after installation or Malfunctioning condensate pump.

Understanding Window Air Conditioners Drain.

Before delving into the potential causes of AC leaks, it’s beneficial to have a grasp of how window air conditioner’s function. A window AC unit comprises three primary components:

  • The evaporator coil, situated on the interior side of the unit, absorbs heat from the air and transforms it into a liquid.
  • The condenser coil, positioned on the exterior side, expels the heat outdoors.
  • A compressor circulates refrigerant between the evaporator and condenser coils.

During operation, the evaporator coil becomes very cold, causing the moisture in the air passing over it to condense.

This condensed moisture must be directed out of the unit. One of the most prevalent reasons for water leaks is a blocked drain.

Related Post>>>Furnace leaking water.

Why Window AC Unit Leaking Water Inside.

There are a several common issues that can lead to water dripping from a window air conditioner:

1.Clogged drain.

One of the primary reasons for a window AC unit leaking water inside is a clogged condensate drain. This drain is essential for removing the water that forms as a result of the evaporator coil’s cooling process.

Over time, this drain can become obstructed by the accumulation of algae, mold, and sediment. When the drain line gets clogged, water can back up within the unit and ultimately leak from the base of the AC unit or even into the wall and room.


To prevent and remedy this issue, follow these steps:

  1. Regular Maintenance: It’s crucial to perform routine maintenance on your window AC unit. Check the drain line periodically, especially before the cooling season begins.
  2. Clear the Drain Line: Start by locating the drain line, which is typically a small PVC pipe or tube connected to the base of the unit. Carefully detach it if necessary.
  3. Flush the Drain: Using a wet/dry vacuum or a can of compressed air, you can attempt to clear the clog from the drain line. Be gentle to avoid damaging the line.
  4. Clean the Drain Pan: Remove any debris or standing water from the drain pan, which is typically located at the bottom of the AC unit.
  5. Use a Drain Cleaner or Vinegar Solution: To prevent future clogs, periodically flush the drain line with a mixture of equal parts water and vinegar or a commercial AC drain cleaner. This helps to dissolve any accumulated grime and keep the drain clear.
  6. Check the Exit Hole: Ensure that nothing obstructs the exit hole where water drains out of the base pan. Sometimes, debris or dirt can accumulate here, causing water to back up.

Regular maintenance and keeping the drain line clear will help prevent water from leaking inside your room and causing potential damage. It’s a relatively simple but crucial step in maintaining your window AC unit’s efficiency and preventing leaks.

2.Improper installation.

Another common reason for water leakage from a window AC unit inside the room is improper installation. If the unit is not installed correctly, it can result in gaps or tilting that allow condensed water to overflow. Proper installation is crucial for ensuring that water drains as intended.


To address this issue and ensure proper installation, follow these steps:

  1. Check for Gaps: Inspect the window opening and the area around the AC unit. Make sure there are no gaps or spaces that could allow water to escape into the room. Seal any gaps with weatherstripping or foam insulation to create a tight fit.
  2. Ensure Proper Tilt: The window AC unit should be installed with a slight downward tilt toward the outside. This ensures that water naturally flows towards the drainage hole and doesn’t pool inside. Use a level to confirm that the unit is installed with the correct slope.
  3. Secure the Unit: Ensure that the AC unit is securely wedged into the window opening. Use the provided mounting brackets or supports to hold it in place. Double-check that it’s not loose or wobbly.
  4. Inspect Side Panels: Check that the side panels of the AC unit are properly inserted and sealed. They should create a snug fit to prevent warm air from entering and cold air from escaping, which can lead to excess condensation.
  5. Seal Any Gaps: If there are gaps around the sides or top of the AC unit, use appropriate sealing materials to close them. This will help maintain the insulation and prevent water from seeping into the room.

Proper installation is crucial in ensuring that your window AC unit operates efficiently and doesn’t cause indoor water leakage.

By following these installation guidelines and addressing any gaps or tilting issues, you can prevent water from spilling inside your room and maintain a comfortable environment.

3.Dirty air filters.

Another significant factor that can lead to water leakage from a window AC unit inside the room is dirty air filters. Clogged air filters can impede proper airflow, resulting in decreased unit efficiency.

When airflow is restricted, it can cause the evaporator coils to develop ice buildup. Once the ice melts, the excess water can overflow from the base pan, leading to leakage.


To address this issue and prevent water leakage due to dirty air filters, follow these steps:

  1. Regular Filter Inspection: Make it a habit to inspect the air filters in your window AC unit regularly, ideally on a monthly basis. The frequency may vary depending on usage and local conditions, but monthly checks are a good general rule.
  2. Filter Replacement: If you notice that the filters are dirty, clogged, or covered in dust and debris, it’s time to replace them. Most window AC units use disposable filters that are easy to replace.
  3. Proper Filter Sizing: Ensure that you select the right-sized replacement filters for your specific AC unit. Refer to the manufacturer’s instructions or check the old filter for size specifications.
  4. Proper Installation: When installing the new filters, follow the manufacturer’s guidelines to ensure they are correctly placed in the unit.
  5. Regular Maintenance: Continue to monitor and replace the filters as needed. Clean filters allow for better airflow and prevent the formation of ice on the evaporator coils.

By maintaining clean and unobstructed air filters in your window AC unit, you can promote proper airflow, enhance unit efficiency, and prevent ice buildup that can lead to indoor water leakage.

This simple maintenance task not only prevents leaks but also helps your AC unit operate effectively and efficiently, keeping your room cool and comfortable.

Also read>>>>Furnace leaking water when ac is on.

4.Low refrigerant levels.

Low refrigerant levels in a window AC unit can result in insufficient cooling and dehumidification of the air. When the refrigerant is insufficient, the evaporator coil may freeze up, causing a similar problem to that of a dirty filter.

As the ice on the evaporator coil melts, it can lead to water overflowing from the base pan, causing indoor water leakage.


To address low refrigerant levels and prevent water leakage due to this issue, follow these steps:

  1. Professional Inspection: It’s essential to have an HVAC technician inspect your window AC unit to determine the refrigerant levels accurately. This is not a task that can be easily done by a non-professional.
  2. Recharge Refrigerant: If the technician identifies low refrigerant levels, they will recharge the system with the appropriate refrigerant type and quantity. This process should only be performed by a certified HVAC technician to ensure it’s done correctly and safely.
  3. Regular Maintenance: To prevent future refrigerant leaks or low levels, schedule regular maintenance for your window AC unit. This includes checking for and addressing any refrigerant leaks, which can occur over time.
  4. Correct Any Leaks: If the technician discovers a refrigerant leak during the inspection, they will need to locate and repair it to prevent ongoing issues.

Low refrigerant levels can have a significant impact on the performance of your window AC unit, leading to issues such as water leakage and reduced cooling efficiency.

By having a professional HVAC technician assess and recharge the refrigerant as needed, you can ensure that your AC operates at its best and prevents indoor water leakage caused by frozen coils. Regular maintenance and leak repairs are key to preventing this problem from recurring.

5.Malfunctioning condensate pump.

In some modern AC units, a small condensate pump is utilized to remove accumulated water efficiently. However, if this condensate pump malfunctions or its drain line becomes obstructed, excess water can spill into the base pan and ultimately lead to leakage inside the room.


To address the issue of a malfunctioning condensate pump and prevent water leakage, follow these steps:

  1. Inspect the Pump Tubing: Examine the tubing connected to the condensate pump for any kinks, bends, or obstructions. These issues can impede the flow of water and lead to pump malfunctions.
  2. Test the Pump: Check the condensate pump’s operation by pouring a small amount of water into the condensate pan or tray. The pump should activate and pump the water out through the drain line. If the pump doesn’t work as expected, it may need repairs or replacement.
  3. Clear Obstructions: If you discover any obstructions in the pump’s drain line, carefully remove them to ensure proper drainage. Clean any debris or blockages that may be affecting the pump’s performance.
  4. Professional Repair or Replacement: If you’re unable to resolve the issue yourself or if the pump requires repair or replacement, it’s best to contact a professional HVAC technician. They can diagnose the problem and either fix the pump or replace it with a functional one.

A malfunctioning condensate pump can disrupt the efficient removal of water from your AC unit, potentially leading to indoor water leakage.

By inspecting the pump tubing, testing the pump, and ensuring there are no obstructions, you can maintain proper drainage and prevent water from spilling into your room.

If necessary, seek the expertise of a professional technician to address any pump-related issues effectively. Regular checks and maintenance will help keep the condensate pump working as intended.

6.Leakage after installation.

In the case of newly installed window AC units, water leakage issues may arise if the rubber gaskets around the chassis fail to create a proper seal.

When these gaskets don’t seal correctly, water can infiltrate and lead to indoor leakage. This problem often occurs due to insufficient sealing during the installation process.


To address leakage issues after the installation of a window AC unit and prevent water from entering your room, follow these steps:

  1. Tighten Installation Bolts and Brackets: First, ensure that all installation bolts and brackets are securely fastened to hold the unit in place. Loose or improperly secured hardware can create gaps that allow water to seep through. Tighten them as needed to achieve a snug fit.
  2. Inspect Rubber Gaskets: Examine the rubber gaskets around the chassis of the AC unit for any signs of damage or wear. If you identify any issues with the gaskets, they should be replaced to restore the seal’s effectiveness.
  3. Apply Weatherstripping: To achieve a watertight seal and prevent any potential gaps, consider using weatherstripping. Apply it around the perimeter of the window frame where the AC unit sits to enhance the seal and prevent water intrusion.
  4. Double-Check Installation: Review the installation process, ensuring that the window AC unit is placed securely and evenly within the window opening. Proper alignment is essential for maintaining a watertight seal.
  5. Seal Any Gaps: Inspect the area around the AC unit for any gaps or openings. Seal these with appropriate materials, such as foam insulation or additional weatherstripping, to further prevent water leakage.

By addressing issues related to inadequate sealing during installation and taking the necessary steps to improve the seal, you can prevent water from entering your room through the window AC unit.

Properly secured hardware, intact rubber gaskets, and additional weatherstripping as needed are key elements in ensuring a watertight installation and avoiding indoor water leakage.

Also read>>>>Air Conditioner Leaking Freon.

Frequently Asked Question (FAQs).

Why is my window AC unit leaking water inside my room?

  • Clogged Drain: One common cause is a clogged condensate drain. Over time, algae, mold, and sediment can block the drain line, leading to water backup. Regularly flush the drain line with a mixture of water and vinegar or a commercial AC drain cleaner to prevent clogs.
  • Improper Installation: If the unit is not correctly installed with a slight downward tilt and gaps are present, water can spill inside. Ensure proper installation, seal gaps with weatherstripping, and maintain a slight tilt towards the outside.
  • Dirty Air Filters: Clogged air filters restrict airflow, causing ice to form on the evaporator coils. When the ice melts, it can lead to water overflow. Check and change air filters monthly to maintain proper airflow.
  • Low Refrigerant Levels: Low refrigerant levels can result in frozen coils, leading to water leakage when the ice melts. Have a professional HVAC technician check and recharge the refrigerant if needed.

What can I do to fix a clogged drain in my window AC unit?

  • Regularly inspect the drain line for clogs, especially before the cooling season.
  • Carefully detach the drain line if necessary.
  • Attempt to clear the clog with a wet/dry vacuum or compressed air, being gentle to avoid damage.
  • Remove any debris or standing water from the drain pan.
  • Periodically flush the drain line with a mixture of equal parts water and vinegar or a commercial AC drain cleaner.

How can I prevent water leakage due to dirty air filters in my window AC unit?

  • Inspect the air filters regularly, ideally on a monthly basis.
  • Replace the filters if they are dirty, clogged, or covered in dust and debris.
  • Use the right-sized replacement filters for your AC unit.
  • Properly install the new filters following the manufacturer’s instructions.

What should I do if my window AC unit leaks water shortly after installation?

  • Tighten all installation bolts and brackets to ensure a secure fit.
  • Inspect the rubber gaskets around the chassis for any damage and replace them if needed.
  • Consider applying weatherstripping around the window frame where the AC unit sits to enhance the seal.
  • Double-check the unit’s placement to ensure it’s evenly and securely installed within the window opening.
  • Inspect the area around the AC unit for gaps and seal them with foam insulation or additional weatherstripping as necessary to prevent water leakage.


Understanding the causes of water leakage from a window AC unit and knowing how to address these issues is essential for maintaining a comfortable and damage-free environment.

Whether it’s due to a clogged drain, improper installation, dirty air filters, low refrigerant levels, or malfunctioning components, prompt action and regular maintenance can prevent water from infiltrating your room.

By following the provided solutions and taking preventive measures, you can ensure the efficient operation of your AC unit, maintain a proper seal, and avoid the potential consequences of water damage and mold growth.

A well-maintained window AC unit not only keeps you cool but also preserves the integrity of your living space.