Why is there water leaking from my furnace?
A high-efficiency furnace produces condensate as a normal by-product, so water around it almost always means that drainage has failed — a blocked drain line, a cracked trap, or a failed condensate pump. Left alone it will usually trip a safety switch and shut the furnace off, which is the system protecting your floor.
Need someone now?
24/7 emergency service · Fredericton and southern New Brunswick
What you can safely check
- Shut it off at the thermostat
- Stop making more condensate while the drainage is blocked.
- Mop up and find the source
- Dry the area and watch where the water actually appears — the drain, the pump, or the cabinet itself.
- Look at the condensate pump
- If there's a small pump, check it has power and isn't full to the brim and silent.
- Protect the area
- Move anything on the floor that water would ruin, and towel around the base.
What’s probably going on
- Blocked condensate drain
- Algae and sludge build in the line over seasons and eventually stop it entirely.
- Cracked or dry trap
- The trap keeps flue gases out of the drain. Cracked, it leaks water and compromises that seal.
- Failed condensate pump
- When the furnace sits below the drain, a pump moves the water. When it fails, the pan overflows.
- Humidifier
- Where one is fitted to the ductwork, it's a frequent and often overlooked source.
Stop here and call
If water is anywhere near the electrical side of the furnace, shut the breaker off and call. Water and the control board are a bad combination.
What we do about it
We clear and flush the drain line, replace the trap if it's cracked, test the pump and the float switch, and check the humidifier where there is one.
Still stuck?
Tell us what the system is doing and we’ll tell you what it takes to fix — free quotes, no obligation, and a straight answer about whether it’s worth repairing.