I have water accumulated in my basement, that I squeezed out using towel. It was about 8 gallons of water in all. The only source I can see is the furnace whose surrounding is wet but I have never seen a running water from there other than being wet.

Previously (last year) I have seen water accumulated once due to what I thought was excessive rains but this time, it has been very dry outside.

Does this picture tells anything if this is the furnace indeed? Is the fix easy?

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I followed up with the answer and filled condensation pump with water. The motor does start and the tank gets emptied but what I noticed is the water starts to seeps through the furnace. I have provided pictures with red circles where water seeps.

It was difficult to determine if the water really gets out through the transparent hose which is very yellowish at this point. I watched several videos on youtube and typical issues seems to blockage of valve. Now I am not sure if that's the case given the water seeps through the furnace after pump action? Could the pump be pushing it in backward direction due to blockage?

Do you think there is still good chance I check for blockage and that could fix the issue or get new pump?

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Update 2

I troubleshooted further and opened the condensation pump. The tank was extremely dirty dust collected over time over time and stuff hanging to walls and floaters. I guess that could block the valve if this stuff is getting pushed out.

I clean it, cleaned the valve and tested the condensation pump by itself and it's working great. When I fill it, the springs up the water with nice power as i have seen in youtube videos.

I put it back but unfortunately, this still didn't fix the issue! The water oozed out from furnace parts higher up after pump action.

  • Do you have a built-in humidifier or central air as part of the system?
    – J Crosby
    Jul 9, 2019 at 17:23
  • 4
    That white and black box on the side is a condensate pump, right? Does that work?
    – JPhi1618
    Jul 9, 2019 at 17:26
  • 2
    Pour some water into the hole on top of the white box (the condensate pump reservoir) and see if it empties out. 8 gallons is a lot. How long did that take to accumulate?
    – isherwood
    Jul 9, 2019 at 17:30
  • Furnace or boiler ? Boilers use water. Make and model of the unit would be helpful and a photo showing more of the unit.
    – Alaska Man
    Jul 9, 2019 at 17:31
  • 1
    When i here the word furnace i think of a forced air heating where a gas fired burner heats air ( not water ) and the air is blown through the house in ducts, no water used unless there is a humidifier that is installed in ducting. We need to know more information. If there is a leak in your plumbing we need to know how and why things are plumbed with water.
    – Alaska Man
    Jul 9, 2019 at 17:54

1 Answer 1


In a comment you said,

AC unit is outside.

Assuming you're talking about a whole-house AC unit, what's outside is the condenser. There's another half to the system - the evaporator. it sits inside your "furnace" and cools the air forced over it by the circulation fan in your furnace, which in turn circulates through your ducts and cools your house.

AC evaporators tend to collect significant condensation, to the point that furnaces with AC fitted will always have a condensate pump to collect and dispose of the condensation. You said you mopped up about 8 gallons of water - where I live, that would be a fairly typical volume for a few days of cooling in a typical home. In other words, it's not really that much.

As mentioned by comments, the white box on the side of your furnace is the condensate pump. The hard white plastic plumbing going into the top of the pump is the drain line, which drains the condensate from the evaporator coils into the pump. The pump has a switch inside it that turns on as it fills with water, and the water is pumped out through the smaller-diameter translucent hose coming out the top of the pump. A good place to start troubleshooting this problem is to pour water in one of the empty holes on the top of the unit, and see if it runs and empties itself out.

If it does not run, make sure it's plugged in and has power. If it is, the pump or the switch inside it may be dead. It's not expensive to replace a condensate pump.

Condensate pumps have a check valve on the fitting for the output line, it's possible the check valve is full of debris or clogged and causing the pump to overflow even if it's running. So check that as well, if you can't troubleshoot otherwise.

If the pump is clean and functional, you may have a problem inside your furnace - the tray that collects condensate from the evaporator coil may be damaged (rusted, or there may be debris collected on it that's causing it to overflow instead of properly drain. If you're not comfortable opening the furnace up to check for these problems, it may be time to call a professional.

  • 1
    Thanks, I think you are on to it, that makes sense. Yes the AC unit outside cools the entire house via the furnace blowing cold air. Your answer is a good start, will follow up on it.Thanks!
    – zar
    Jul 9, 2019 at 18:29
  • I updated the question, added more details after your suggestion. Please check.
    – zar
    Jul 11, 2019 at 14:22
  • It's hard to tell from your photos what the general orientation of your unit is, but I would guess the AC evaporator is in the upper section next to where the leaks are. It sounds like the water that makes it to the pump is not being pumped out properly, and the drip tray under the evaporator is probably full and overflowing. If I were you, I would pull the pump apart, check for blockages or a stuck check valve, and check the hose for blockages. Find the other end of the hose and see if water comes out - the hose probably terminates in a floor drain, sump pit, or standpipe somewhere.
    – dwizum
    Jul 11, 2019 at 14:29
  • Also this should be obvious but make sure that drain line is intact and positioned correctly. I've seen installs where someone just sort of looped it up over duct work or other infrastructure and dangled the end into a drain, such that even a gentle tug would cause the end to pop out and water is now just being indiscriminately dumped onto the floor or the furnace or somewhere else you don't want it.
    – dwizum
    Jul 11, 2019 at 14:31
  • The problem is fixed. The drain to condensation pump was clogged. Cleaning that up fixed the issue. This was essentially in the U shaped area of drain which I guess is designed to collect dust particles/floaters.
    – zar
    Jul 19, 2019 at 13:59

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