You've got a puddle around the base of the furnace. Could be a few things – depends on whether it happens in cooling season, heating season, or both.
You probably came here because…
- Water pooling on the floor around the base of the furnace
- May happen in summer only, winter only, or year-round
- You may notice rust developing on the bottom of the furnace cabinet
- The furnace or AC may be shutting itself off (float switch tripping)
What’s actually happening
Water around the furnace has different causes depending on the season. In summer, it's the AC's condensate drain (the AC's evaporator coil sits on top of most furnaces, and water drips down through the cabinet if the drain fails).
In winter, if you have a high-efficiency (condensing) furnace – the kind that vents through PVC pipe out the side of the house – the combustion process actually produces water as a byproduct. That water drains through its own condensate line. If that line clogs, you get a winter puddle.
Non-condensing furnaces (metal flue up through the roof) don't produce condensate in heating mode, so a winter puddle on those is usually a humidifier leak or a plumbing leak from above.
What we do about it
Note the season
Track when the water shows up. Summer only = AC drain. Winter only = furnace condensate (if you have a high-efficiency unit) or humidifier. Year-round = plumbing leak from above.
Locate all drain lines
There may be 2-3 PVC drain lines coming out of the furnace: one from the AC coil above, one from the furnace itself if it's high-efficiency, and one from the humidifier if you have one. Trace each to where it terminates.
Clear the appropriate line
For AC drain, use a wet/dry vac on the outside end or pour vinegar in the cleanout. For furnace condensate, same approach. Humidifier drains rarely clog – they just fail at the humidifier.
When to just call
If your furnace has visible rust on the bottom cabinet, the water has been leaking for a while and internal parts may be damaged. If it's a high-efficiency furnace with a clogged condensate line, running it that way can flood the burner box. Call (423) 637-1846.
Ready to fix it?
Call the family that’s been doing this in the Sequatchie Valley since 1996.