When a simple water leak becomes a nightmare for homeowners
At AirGreen, we intervene every week in Montréal, Laval, Longueuil, the North Shore and the South Shore to fix problems related to wall-mounted air conditioners that leak water. This issue, much more common than people think, is often underestimated… until it causes water damage to walls, ceilings, or even hardwood floors. Recently, we were called to Longueuil to resolve a critical situation: a GREE Lomo 12,000 BTU wall-mounted air conditioner had been leaking for several weeks, compromising the integrity of a newly renovated condo.
Our team not only identified the root cause of the problem but implemented a permanent solution, ensuring optimal performance of the unit for years to come.
Why does a wall-mounted air conditioner start leaking?
The most common causes we see in the field
In nearly 80% of cases, water leaks are due to a drainage issue:
-
Clogged drain caused by dust, pet hair, mold, or algae.
-
Improper slope of the indoor unit from the original installation.
-
Excessive condensation due to a dirty filter or poorly regulated low temperature.
-
Poorly insulated or damaged drain hose, causing backflow.
-
Faulty condensate pump in vertical or condo installations.
During our Longueuil service call, we quickly discovered that the drain hose had been poorly connected during the initial installation by an inexperienced company, causing constant backflow into the indoor casing.
Case study: AirGreen intervention in Longueuil for a GREE wall-mounted air conditioner
Fast diagnosis, precise intervention
Upon our arrival, the client explained that several contractors had come to “clean” the unit, but the problem was never resolved. Water continued to seep along the wall, damaging the paint and causing bubbles in the drywall.
Our team proceeded with a full disassembly of the wall unit to analyze contact points, slope, condensate tray sealing, and the condition of the drain hose. We discovered:
-
The drain had been installed too high, preventing natural water flow.
-
A poorly sealed elbow joint was leaking inside the wall.
-
The filter was clogged, promoting moisture buildup.
The solutions implemented by AirGreen
We carried out the following actions:
-
Complete reinstallation of the wall unit with an optimal backward slope of 5 to 10 mm.
-
Replacement of the drain hose with a flexible, insulated pipe resistant to temperature changes.
-
Tight sealing of all joints using specialized HVAC-grade PVC tape.
-
Addition of a backflow prevention trap, ensuring smooth drainage.
-
Thorough cleaning of the blower and condensate tray using antimicrobial solution.
-
Installation of an accessible maintenance hatch, simplifying yearly servicing.
Why choose AirGreen to fix water leaks in your wall-mounted air conditioner?
A methodical approach, backed by field experience
We don’t just clean a drain or add a bit of silicone. At AirGreen, we analyze the entire HVAC system, from the original installation to the smallest pipe connection. Every intervention starts with a structured diagnosis, including before/after photos, a written report, and tailored recommendations.
Expertise with the most common brands
Our technicians are fully trained to work on all major wall-mounted air conditioner brands used in the Greater Montréal area:
-
GREE Lomo, Gree Extreme, Gree Sapphire
-
Fujitsu KZAS, KZAH
-
Mitsubishi Mr. Slim
-
Tosot and Sharp ZU1
-
Senville Leto and Aura
We know their weak points, their design flaws, and the best practices to ensure long-term reliability.
Tips to prevent water leaks in your wall-mounted air conditioner
Annual HVAC maintenance: the key to longevity
One of the best ways to avoid issues is to schedule a complete HVAC service in the spring, before the peak summer heat. This includes:
-
Cleaning of the filter, blower, and condensate tray.
-
Inspection of the drain hose and its slope.
-
Testing of the pump (if applicable).
-
Checking refrigerant pressure.
Common mistakes to avoid
-
DIY wall unit installation without a level or understanding of condensate flow.
-
Using household silicone instead of certified HVAC materials.
-
Neglecting the air filter: a clogged filter causes excessive condensation.
-
Blocking the drain line in winter, leading to backflow in spring.
Customer testimonial: “AirGreen were the only ones who found the real cause”
Ms. Laporte, owner of the condo in Longueuil, shared this testimonial with us:
“I was desperate. Every summer, it was the same thing. Water everywhere. I paid three contractors for nothing. AirGreen took the time to disassemble, analyze, and explain. They fixed everything from A to Z, and for the past two years, I haven’t had a single drop of water.”
Why this type of article matters to you
By sharing our real-life experiences in the field, we help you better understand the issues linked to your wall-mounted air conditioning system, while giving you practical solutions, tested and proven. It’s part of our mission: to offer transparent, expert, and human HVAC service throughout the Greater Montréal area.
We encourage you to contact us at the first signs of moisture. A small leak can hide a much larger structural problem if not handled quickly.
Contact AirGreen for an inspection or preventive maintenance
Whether you’re in Montréal, Laval, Longueuil, the North Shore, or the South Shore, our team is available to intervene quickly, with expertise and precision.
A wall-mounted air conditioner should never leak. With AirGreen, it never will again.