How the Condensate Drain Works
When your heat pump runs in cooling mode (or dehumidifies), the indoor coil gets cold and pulls moisture out of the air. That moisture condenses into water, drips into a drain pan beneath the coil, and flows out through the condensate drain line — usually a length of PVC or vinyl tubing that leads outdoors or to a floor drain.
If the indoor unit sits below the drain's exit point, a small condensate pump lifts the water up and out instead of relying on gravity. Either way, the goal is the same: capture every drop of condensation and carry it safely away from your home.
It's a simple system, but it handles a steady stream of water during humid weather — which is exactly why a small blockage causes such an obvious leak.
Why Condensate Drains Leak
Algae and slime buildup is the leading cause. The drain line is dark, damp, and full of slow-moving water — ideal conditions for biological growth. Over a season or two, that slime can fully block the pipe, and water backs up over the drain pan.
A clogged or dirty drain pan. Dust and debris settle in the pan and clog the drain opening, or the pan itself rusts and cracks with age.
A failed condensate pump. If your system relies on a pump and it stops working — a stuck float, a burned-out motor, a tripped breaker — the reservoir fills and overflows.
A disconnected or poorly sloped line. A drain line that's been bumped loose, or one that was never pitched to drain downhill, will let water sit and spill.
A frozen line in cold weather. An outdoor section of drain line can freeze in a Lower Mainland cold snap, blocking flow until it thaws.
Safe DIY Checks
Some condensate issues are within reach for a careful homeowner. Start by turning the system off so you're not adding water while you work. Then check the drain pan — if it's full or you see standing water, the drain is blocked.
If you can access the drain line cleanout (often a capped T-fitting near the indoor unit), you can gently flush it with warm water and a splash of white vinegar to break down early slime. Some people use a wet/dry vacuum at the outdoor end of the line to pull a clog free. If your unit has a condensate pump, check that it has power and that the float isn't stuck; emptying and cleaning the reservoir sometimes gets a stalled pump going again.
What to leave alone: anything involving the sealed refrigerant system, electrical repairs, or a pan replacement. If the line is fully blocked, the pump is dead, or the pan is cracked, that's a job for a technician.
BC Climate and Condensate Problems
Greater Vancouver's humidity works the condensate system hard. During muggy summer stretches, an indoor coil can produce a steady flow of water all day, so drain lines here fill, foul, and clog faster than they would in a dry climate. Annual cleaning of the drain line and pan is genuinely worthwhile in the Lower Mainland.
Winter brings the opposite challenge. An outdoor portion of condensate line can freeze during a cold snap, blocking flow until temperatures rise. And meltwater from the outdoor unit's defrost cycle, if it can't drain away from the unit, may pool and refreeze into an icy hazard near doorways or walkways.
None of this is cause for alarm — it's just our coastal climate. But it does mean condensate maintenance deserves a spot on your seasonal home checklist.
When to Call CanroHeat
Heat pumps for GasBoilers.ca are serviced by our parent company, CanroHeat, with technicians covering heat pumps, furnaces, and water heaters across Greater Vancouver. If a flush doesn't clear the drain, the pump won't run, the pan is cracked, or water keeps coming back, call 604-359-1081.
A technician will fully clear the drain line, repair or replace a failed pump or damaged pan, confirm the line is properly sloped and connected, and make sure a safety float switch is working so the system shuts off rather than flooding if it ever clogs again. A quick condensate fix is one of the most affordable heat pump repairs there is — and well worth doing before water damages your floors. Call 604-359-1081 to book.