Furnace Exhaust Fan Full Of Water

First remove the drain tube and fitting.

Furnace exhaust fan full of water.

You can prevent slime and eliminate drain tube clogs in two easy steps. Slope the drain line itself obviously. The fan assist is meant to help with the natural draft not pressurizing the exhaust pipe with a power vent fan found in condensing furnaces and discussed below. You can identify a condensing furnace by the pvc vent pipe that allows exhaust gases to exit the appliance after they have cooled down.

Look in your install manual most manufacturers will call for the furnace to be installed with a slight forward pitch to allow condensate to drain from the heat exchanger. Avoid double trapping and vent the drain after the trap to prevent airlocks. Look inside of the blower box for water accumulation. A standard efficiency furnace extracts some heat from the combustion gases and quickly vents them out the exhaust or flue pipe.

If you have a condensation leak with a standard efficiency then its exhaust or flue pipe may be incorrectly sized. Condensation from air conditioning coils contains bacteria that can form slime and clog the condensate pan drain tube. If there is water in the blower box contact a professional repairman to replace the blower box and silver bladder. Water may accumulate due to a broken silver bladder or faulty insulation.

Most furnaces will have at least 2 internal drains typically one for the heat exchanger and one for the vent usually at the inducer outlet or on the inducer housing the secondary heat exchanger outlet is sealed inside a plastic part called the collector box which is designed to collect the condensate and drain it out if the seal gets damaged the water will fill the inducer. As the exhaust gases cool down during the primary and secondary heat extraction water usually condenses and flows out of the furnace.