Symptom
Water around a condensing furnace
Water around a condensing furnace almost always means the condensate path is blocked, frozen, disconnected or mis-routed. The furnace may keep running for a while, then stop with a pressure-switch or drain code, or the water may simply appear and keep coming.
Short answer
Find where the water is coming from before mopping: the condensate drain or pump, the trap, a vent pipe, or the furnace cabinet. If a condensate pump is overflowing, switch the furnace off at the thermostat, unplug the pump if it is accessible, and call. Do not open the trap on a running furnace; it is part of the flue-gas seal. Water alone is not a gas emergency, but a furnace whose condensate system has failed should be taken out of service until it is fixed.
Have a code on the display?
Why condensing furnaces make water
Every furnace sold new in Canada is at least 95% AFUE, which is only possible by cooling flue gas until its water vapour condenses. That water is mildly acidic and must drain continuously through the trap and drain. The trap is also part of the flue-gas seal, which is why opening it is a technician's job.
Where the water comes from
A blocked trap or drain backs water into the furnace and out around the cabinet. A failed or overflowing condensate pump leaks from the pump. A vent pipe that is sagging or frozen drains back and leaks at fittings. And in very cold weather, an exterior drain termination can freeze and back the whole path up.
What the furnace does next
When water backs into the collector box, the pressure switch cannot prove draft and the furnace stops with a pressure-switch code, or it locks out after repeated events. Some controls log the drain fault separately. The water is the cause; the code is the effect.
Related
- ServiceGas Furnace RepairFurnace repair in Greater Vancouver, diagnosed before parts are replaced
- ServiceCondensate ManagementCondensate done right: drains, traps, pumps and winterization
- ServiceFurnace MaintenanceAnnual furnace maintenance that checks what actually fails
- ComponentCondensate trap, drain and pump
- ComponentFurnace pressure switch
- SymptomFurnace not heating
Questions people ask
Is the water dangerous?
Condensate is mildly acidic and can damage flooring and rust equipment, but it is not a gas or CO hazard by itself. The danger is running a furnace whose trap is not sealing, so the repair is left to a technician.
Can I unclog the condensate line myself?
Clearing the drain line where it is accessible, such as removing a blockage at the termination, is reasonable; opening the trap or the collector box on a gas appliance is not. When in doubt, call.
Why does water appear only in cold weather?
Cold-weather condensate failures come from freezing: a drain through unheated space, an exterior termination that ices over, or a vent that holds water and freezes. Manufacturers specify winterization where drains can freeze.
Still no heat?
Call BC Wide with the brand, model number and anything on the display. Or
Request service online with this page attached.