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Condensate furnace drain line freezing


We have a condensate furnace and a small sump pump located at the base that pushes water up (from a collection pan on the basement floor) and out of the house. The tygon tubing line, as it exits the basement, keeps freezing (as it is cold in Ct winters). Since it freezes, the water can not drain and the pan overflows into the basement.

I have two questions. How am I going to prevent this from continuing to freeze all winter?

Why is my furnace removing moisture from the air? We run humidifiers all winter because the air gets so dry. Sholdn't my furnace help regulate the humidity to a comfortable level in winter? What can I do? (ok more that 2 questions)

Thanks for your time.

Re: Condensate furnace drain line freezing

I think some heat tape somewhere near the outside exit should help keep it from freezing.
Or reroute the drain as a temporary measure to a bucket that you can empty. I'm sure that would get old fast.

It sounds like your furnace is a newer high efficiency furnace. The moisture is condensing out of the exhaust gasses because the furnace is wringing out so much heat from the fuel. In less efficient furnaces, the moisture just goes up the flue.
Your furnace most likely has an outside combustion air intake so it isn't taking anything out of your house.
Your house is dry because you are taking 20 or 30 degree air that doesn't hold much water vapor & heating it to 70 degrees or so. The 70 degree air can hold a lot more water, so the relative humidity drops dramatically in the heated air.
The only way to regulate the RH in the winter is to add more water to the air with humidifyers like you are doing.

Re: Condensate furnace drain line freezing

The water you're seeing is not from the air inside your home, but rather is coming from the cooled flue gases inside the heat-exchanger of your high-efficiency (condensing) furnace.

Evidently there is no washing machine with stand pipe down there, or sinks, floor drains, etc....... and so the furnace installer took this route for the condensate line. ???

Are there any "horizontal" drain lines down there.... overhead, so to speak?

A little more info, if you would, before we take time trying to offer up possible resolutions.

Oops. While I talked on the phone, Ed posted.

Heat tape on plastic lines is a no-no. So you'd have to transition to metal a few feet before exiting the house. I guess I'd personally prefer to find some solution that isn't reliant upon yet another "device", if possible.

Re: Condensate furnace drain line freezing
goldhiller wrote:

Heat tape on plastic lines is a no-no. So you'd have to transition to metal a few feet before exiting the house. I guess I'd personally prefer to find some solution that isn't reliant upon yet another "device", if possible.

I'll take your word on it having never actually installed any.:o
I agree avoiding another device is desirable.
Maybe transitioning to a larger diameter pipe where it exits the house would be less likely to freeze up & block the flow.

Re: Condensate furnace drain line freezing

Thank you for your comments so far.

The main drain line that leads out to the septic system is about 20 or so feet away from the furnace. Im not sure if the pump that is there would have enough head pressure to get the condensate water to it, but I did think it may be a possible solution.

I also think the idea of increasing the diameter is a good one. That is something I can do.

What advice do you have on using some if this moisture, putting it back into the house? Is there an add-on system that I could ask a professional installer about?


Re: Condensate furnace drain line freezing

I wouldn't even consider using that water for house humdification. It is afterall, moisture from the flue gases of the furnace.

To the best of knowledge (and my HVAC supply house)......there are no nifty dedicated devices to deal with the problem you're experiencing. Wish there was because you're not the only person to experience this problem.

I was hoping for a drain line of a smaller diameter than the main house drain....which is likely 4". Something on the order of 1 1/2" - 2" would be somewhat easier to deal with. However, if that's not available, it isn't. Basic idea would be to cut into that line and install a P-trap with a standpipe. Then mount the condensate line so the end is over this trap, but NOT in it. You need to keep an air gap between the two. 2" or so should be fine.

Not absolutely sure if this arrangement would "make code" in your locale or not. One potential consequence would be that if your septic backs up....."stuff" would emerge from this trap before any other fixture in the house. Then again, if you had a washing machine with a trap and standpipe down there, you'd have the same result. Personally, if the septic or sewer is gonna back-up, I'd sooner it happened in my basement than in the kitchen or bathroom on the ground floor.

Another potential problem is septic gas entering the basement. During the non-heating months, the water in the trap may evaporate. If that happens, you should smell it and then know it's time to add a couple cups of water to that trap.

As far as the pump having enough guts to get over to that house drain.........just pipe it (with rigid PVC or CPVC pipe) so that the line runs downhill to the trap. Then all the pump has to do is the vertical job and the rest is taken care of by gravity. If your pump is worth a hoot, it should do that......unless you have 12' foot ceilings down there. :)

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