Air filter wet? Water leaking as your furnace is running? There can be a few reasons why this is happening.
If you have a high efficiency furnace, here's the most common reason:
CONDENSATION LEAK
A high efficiency furnace has 2 heat exchangers that results in producing more heat. This allows the furnace to extract heat from the gases for a longer period of time.
This causes the combustion gases to cool and then condense.
The condensation that is produced should exit out your home through a drain. If you notice that water is pooling around the furnace then there is a problem preventing it from draining correctly.
If this is the case, contact your local HVAC expert. Your high efficiency furnace could have breaks in the condensation line, clogged condensation tubing or drain.
Have a standard-efficiency furnace?
This has a metal exhaust pipe — and should not have condensation.
If it does, it could mean that the flue pipe was incorrectly sized. That could allow the hot exhaust to cool down and condense in the pipe, then drain back to the furnace and leak out.
Note: You’ll know if you have a high-efficiency furnace if:
1. The yellow energy guide tag says your furnace’s efficiency is 90% or higher AFUE.
2. The vent/flue pipe is white PVC as opposed to metal.