Why Air Conditioners Produce Water
Definition
Condensation: The process of water vapor in humid air converting to liquid water when it contacts a surface cooler than the dew point temperature. In air conditioning, this occurs on the evaporator coil surface.
Water dripping from your aircon isn't always a sign of malfunction — air conditioners naturally produce condensation as part of the cooling process. When warm, humid Philippine air passes over the cold evaporator coil, moisture in the air condenses into water droplets, similar to how a cold glass of water 'sweats' on a hot day. In the Philippines' high-humidity climate (70-85% relative humidity), a 1.0 HP aircon can produce 1-2 liters of condensation per hour. This water collects in the drain pan beneath the evaporator coil and flows through the drain line to exit the building. When this drainage system is working correctly, you'll never see this water indoors. A leak means something in this drainage path is blocked, broken, or improperly installed.
Clogged Drain Line — Most Common Cause
In over 60% of aircon water leak cases our technicians handle across Metro Manila, the cause is a clogged drain line. The drain line is a small PVC pipe (usually 16-20mm diameter) that carries condensation from the indoor unit's drain pan to an exterior outlet. Over time, algae, mold, dust, and debris accumulate inside this pipe, creating a blockage that causes water to back up into the drain pan and overflow onto your wall or floor. Philippine humidity accelerates this process — the warm, moist environment inside the drain line is ideal for biological growth. Prevention is straightforward: during every professional cleaning visit, have the technician flush the drain line with water and a mild bleach solution. Between cleanings, you can pour a cup of white vinegar into the drain pan access point monthly to inhibit mold growth.
Example
A Taguig homeowner had water dripping from their Panasonic split-type every afternoon during summer. Our technician found the drain line completely blocked with algae buildup after 8 months without cleaning. A 15-minute drain flush solved the problem immediately.
Cracked or Overflowing Drain Pan
The drain pan sits directly beneath the evaporator coil and collects all condensation before routing it to the drain line. In older units (7+ years), the plastic drain pan can develop hairline cracks from thermal cycling — the constant expansion and contraction as the unit heats and cools. These cracks allow water to bypass the drain line entirely, dripping directly from the indoor unit housing. Additionally, if the drain line is partially blocked (not fully clogged), the drain pan may fill faster than it drains, causing overflow during peak humidity hours — typically afternoons in Philippine summer. Drain pan replacement costs ₱1,500-₱3,000 depending on the brand and model. For units older than 10 years, consider replacing the entire unit rather than investing in an aging drain pan.
Improper Installation Angle
Split-type indoor units must be mounted with a slight backward tilt (2-3 degrees toward the wall) to ensure condensation flows by gravity toward the drain pan's outlet. If the unit was installed perfectly level or tilted slightly forward, water may pool at the front of the drain pan and drip from the front of the unit rather than flowing to the drain connection at the back. This installation error is more common with DIY or budget installations that skip proper leveling. The fix requires loosening the mounting plate, adjusting the tilt angle using a bubble level, and re-securing the unit. Mr. Aircon technicians use a spirit level on every installation to verify the correct drainage angle before sealing the unit.
Frozen Evaporator Coil Melting
When ice forms on the evaporator coil and then melts, the volume of water produced can overwhelm the drain pan capacity, causing significant leaking. Ice formation is caused by low refrigerant (indicating a leak), severely clogged filters restricting airflow, or a failing blower fan motor. If you notice ice on the copper pipes emerging from the indoor unit, or water leaking in large quantities rather than a slow drip, turn off the aircon immediately. Allow 2-3 hours for complete defrosting with towels placed beneath the unit to catch melting ice water. After defrosting, clean the air filter thoroughly. If ice returns when you restart the unit, call a technician — the underlying cause (usually a refrigerant leak) requires professional diagnosis and repair.
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Aircon Leaking Water? Causes, Fixes, and Prevention Tips
From the Mr. Aircon Philippines Encyclopedia — Expert HVAC knowledge since 2002.