Guides · 2026-04-23

Why your wall-mounted AC is leaking water

Indoor wall units produce condensate whenever they cool. Under normal conditions water travels through a drain hose to a floor drain or pump. When that path fails, water can spill from the head or seep into the wall.

Ice formation during cooling can also melt suddenly and look like a leak. The right fix depends on whether the issue is mechanical, cleanliness-related, or refrigerant-related.

Clogged or kinked condensate drain

Algae and dust narrow the hose over time. A partial clog lets the pan overflow during heavy runtime—often after humid Montreal days.

Technicians clear the path, verify pitch, and test pour water through the line to prove flow.

Low airflow and frozen coils

A very dirty filter or blower limitation can drive coil temperature low enough to ice up. When the unit cycles off, ice melts and can overwhelm the pan.

Cleaning the coil and restoring proper airflow usually stops the cycle of ice and overflow, but refrigerant checks belong to qualified HVAC work if icing persists.

Installation or insulation issues

Occasionally, condensate forms on a cold line set inside the wall if insulation is damaged. That moisture is not from the pan and needs a different repair plan.

If you notice staining along the line route, mention it when booking so the team allocates time to inspect visible sections safely.

FAQ

Should I turn the unit off if it is leaking?
If water is reaching drywall or flooring, switch cooling off to reduce condensate production and place a towel to protect surfaces. Then book service—hidden moisture can spread quickly.

Is a small drip normal?
A brief drip at shutdown can happen, but steady dripping indoors is not normal. Treat ongoing water as a sign the drain path or airflow needs attention.