OK to terminate furnace condesation tube in sump pit?

Any reason not to terminate the furnace condensation tube at the sump pit?

Perfect place to put unwanted water as long as the sump pumps works

What do you mean by “tube”?

If it is 3/4" pvc coming directly from the unit (not a 3/8" plastic tube from a condensate pump), There should be an air break between the pipe and the pit. Any direct drain should be trapped. But, even with a trap it will dry out in the winter and may entrain crap from the pit like Radon Gas and distribute it throughout the house.

It’s the 3/8" tube coming out of the condensate pump, David. There’s a sump pit 5’ away. Why does it need a trap? I thought traps were just to prevent sewer gas from entering the living space. Does it require a trap to prevent the products of cumbustion from entering the living space? I don’e recall ever seeing a trap on a furnace condensate tube.
Actually the whole venting system seemed to be installed badly and condensate was draining back into the furnace cabinet.

I’m sorry, misunderstood what you were describing! I was thinking A/C condensate. Pictures always help!

You are correct, the exhaust manifold is designed to trap by the mfg.

One note (drift).
A trap is not just required to trap out sewer gas ect…
They are needed for proper operation of the condensate system.
If you do not have a trap on a draw through a/c coil, the condensate may overflow the pan inside the equipment.

What is inside the cabinet below the pipe?
Also, it may be an illusion but the exhaust pipe does not look like it is sloping back to the unit as it should.

Metal cabinet beneath the plastic vent pipe. Improper slope is an illusion from the wide-angle lens.


Looks to me like you are talking about a High-Efficiency (91%+/-AFUE) Condensing Furnace, in a horizontal position, in a crawl space. Lots to consider with this one, but I would call your local HVAC Contr. to get the proper code requirements for acid based condensate disposal.

Many I have seen have an air gap or a vacumn breaker. In Colorado they went to a floor drain or sump pit. Here in Washington they usually will get to a drain.

A lot better then what many do here just drill a hole in the floor and take it straight down with no trap either.

Right on the money, Greg. I did recommend qualified HVAC contractor do an inspection. I wondered what the deal was, model # but no brand name on it. He ran it through the Preston Guide and there was a recall on this 2-year old furnace.

Please Explain.

Most 90+ efficient (condensing gas furnaces) have a built in trap. With A/C coils, a trap must be installed.

So the trap is located at the base of the PVC vent?

I subscribed to the Preston Guide, but when I entered the model number fromthe furnce, it wasn’t in their data base.

There are two styles of air handlers, one pushes air through the air-conditioning coil, the other pulls it through. Pushing causes a positive atmospheric pressure in the drain line and pulling causes a negative pressure in the drain line. The condensate trap is designed to prevent air from passing through the condensate drain in either direction. This trap only remains wet during operation of the air-conditioning (except in the event of a high efficiency furnace which condenses condensate from the combustion gases). When the trap dries out in the winter, there will be air flow. Sump pits are a primary sources of radon infiltration if they are not sealed. If you do not have a proper wet trap installed to the sump you will be sucking air from the pit and it will be distributed through the HVAC supply air system.

Is that what you’re looking for?

This scenario only applies to gravity drains. This is not a concern when you’re discharging from a condensate pump etc.

Also you should note that in the case described in this thread, an air-conditioning drain is not in question. This unit appears to only have a condensate drain for the furnace. High efficiency furnace condensate drains are separated from the supply air system of the furnace by the heat exchanger and any contaminants will not enter the house, rather will be forced out the furnace flue pipe.

Hi Dave!
At first I was concerned by your response that included the comments about the Radon gas. .

I was wondering if you had misunderstood the initial question.

I am glad to see that you are aware that although the condensate line is “draining into the sump pump pit” the condensate line from the high efficiency gas furnace would not be distributing Radon gas throughout the house.