I posted this and the main suspect was condensation pump but after troubleshooting, the pump is working fine (tested standalone). Now I wonder if the leak could be due to the condensation neutralizer; could that get blocked and prevent water from pumping? It that a likelihood?

More details in my the linked post if needed but basically the furnace leaks out water from top section after the pump runs.

1 Answer 1


To me it looks like the drain line is plugged causing the condensate to build up in the air handler. Once the water level is high enough it finds a way out.

You know your pump is working but now you need to make sure to clear the line from the air handler to the pump. It is quite common for dust and spores to develop blockages in the tubing and this creates the problem you have.

There is 1 more possibility that a low Freon charge could be causing the evaporator to ice up and possibly water dripping down the side wall is causing the leak but I would be clearing the drain tube (this is quite a common thing).

  • It make sense the line (I think you mean to the pump) maybe dirty because the condensation pump was extremely dirty with floaters in it. Still not sure if that would cause this issue because water does make it to the condensation pump. But I have removed the condensation pump temporarily and collecting the water in bucket to see if still leaks. My guess is it probably wouldn't but will update how it goes.
    – zar
    Jul 16, 2019 at 14:09
  • Those floaters do cause enough blockage for this to happen, when the ac is running a mid sized unit can produce gallons per hour in humid climates but some water is making it down to the pump this is similar to hair and soap scum blocking a bathroom drain it just drains slow so we quit putting water in the sink, with the ac when it is running it is producing water so the overflow.
    – Ed Beal
    Jul 16, 2019 at 14:22
  • That would mean you would still expect leakage even though I have removed the pump temporarily and collecting water in bucket. I will know by end of the day or tomorrow if leakage continues.
    – zar
    Jul 16, 2019 at 14:55
  • 1
    Yes it will probably still leak.
    – Ed Beal
    Jul 16, 2019 at 14:58
  • 1
    It will probably be ok but keep an eye on it as other “floaters” may be close to the opening. When I service air handlers I usually spray them with a non acid coil cleaner or add sanitizing tablets (required on some commercial jobs to kill legionella bacteria). These treatments also kill the gunkies or keep them from growing.
    – Ed Beal
    Jul 17, 2019 at 16:38

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