Water dripping from your AC indoor unit? Do not panic, but do not wait either. Most causes have a $150 to $450 fix when you call us within a day. A few cause drywall and ceiling damage within hours if you ignore them. Here is the diagnostic our techs run on every Mississauga and Toronto leak call.
First 60 Seconds: Stop the Damage
- Turn the AC off at the thermostat. The leak stops as soon as the coil stops condensing water.
- Place a towel or bucket under the leak to protect flooring and drywall.
- Locate the leak source: indoor air handler, copper lineset penetration, or outdoor unit.
- Take 2 to 3 phone photos before you wipe anything up. They help our tech diagnose remotely.
- Call EcoFrost at (416) 835-4775. We dispatch same-day across the GTA.
7 Reasons Your AC Is Leaking Water
Clogged condensate drain line
The most common cause. Algae and dust build up inside the 3/4 inch PVC drain line over 2 to 4 years and block the flow. Water backs up in the pan and overflows. We clear the line with a wet/dry vac at the outdoor discharge point or with a nitrogen purge from indoors.
Cracked or rusted drain pan
Drain pans last 10 to 15 years. Once they rust through, water drips wherever the crack is. Replacement runs $250 to $450 depending on whether your model has a removable pan or a built-in one.
Failed condensate pump
Basement and attic AC installs that need to pump condensate uphill use a small condensate pump. When the float switch sticks or the motor burns out, the pump stops and the reservoir overflows. Replacement pump installed runs $300 to $500.
Frozen evaporator coil
When refrigerant runs low or airflow is restricted (clogged filter, blocked return), the coil freezes solid. As the unit cycles off, the ice melts faster than the drain pan can handle. The flood looks like a leak but the root cause is low refrigerant or a dirty filter.
Disconnected drain line
PVC connections can wiggle loose over time, especially if a teenager bumps the line carrying laundry to the basement. We re-glue the joint with PVC cement, $150 install.
Improperly installed unit (negative slope)
If the air handler was installed level instead of tilted slightly toward the drain, the pan fills until water overflows the front edge before it reaches the drain. We re-shim the unit to restore the slope, $200 to $300.
High humidity overwhelming the drain
On a humid 30C day, an undersized or aged AC produces more condensate than the drain line can carry. The fix is upsizing the drain line or replacing the AC with a properly-sized variable-speed unit.
Can I Clear the Drain Myself?
Sometimes yes. Attach a wet/dry shop vac to the outdoor end of the condensate drain line (a white PVC pipe that exits the house exterior). Seal the connection with duct tape and run the vacuum for 60 to 90 seconds. Then pour one cup of distilled white vinegar into the access port at the indoor air handler to prevent algae regrowth. If water backs up again within a week, the blockage is deeper in the line and a tech needs to flush it from inside.
Why Frozen Coils Often Look Like Leaks
A frozen coil hides under insulation and looks fine from outside the unit. When the AC shuts off, the ice melts onto the drain pan all at once, overflows, and creates a leak. The root cause is not the drain at all. It is low refrigerant, a dirty filter, or restricted return airflow. We diagnose by checking refrigerant pressure with gauges. If pressure is low, we find and fix the leak, then top up the refrigerant. Quick top-offs on R-410A units run $250 to $450.
How Much Does AC Drainage Repair Cost in Toronto?
| Repair | Typical 2026 cost |
|---|---|
| Drain line clearing | $150 to $250 |
| Drain pan replacement | $250 to $450 |
| Condensate pump replacement | $300 to $500 |
| Refrigerant top-off (frozen coil cause) | $250 to $450 |
| Full evaporator coil cleaning | $400 to $600 |
| Drain line re-piping | $300 to $700 |
When To Replace Instead of Repair
If the coil is rusted through and leaking water from inside the cabinet, the unit is at end of life. Coil replacement on a 12 plus year old AC costs $1,400 to $2,200, which is roughly half of a new AC install. Our techs give you both options in writing during the service call.
Call us at (416) 835-4775 and we will dispatch a same-day truck across Mississauga, Toronto and the GTA.
Book AC Repair?Frequently Asked Questions
How long can my AC run before the leak causes drywall damage?
Is condensate water safe to touch?
Why is my outdoor AC unit leaking water on a hot day?
Will home insurance cover AC water damage?
How do I prevent future AC leaks?
EcoFrost Heating & Cooling
Toronto's Trusted HVAC Experts Since 2015
Our certified HVAC technicians have served 5,000+ Toronto-area homes. We write about heating, cooling, and air quality from real field experience not marketing copy. Learn about us →
