HVAC Question. Condensate drain lines.

[Clarence Martin]

Need to install a condensate drain line on a forced hot air natural gas furnace that was installed in a closet off of the 2nd bedroom on the 2nd floor of the house. The furnace heats the upper part of the house. Lower unit is heated with a gas boiler. Dealing with constant , year round moisture dripping out of the flue pipe. Condensation is created inside the pipe. No cracks in the pipe leaking water in from the outside.

Nearest drain pipe would be the 2nd floor bathroom. Would have to cut through all of the hardwood flooring and walls to get to the tub or sink drain. Don't want to do that.

Couldn't I just install the drain line through the outside wall ? Wall is about 3 or 4 feet from the furnace. The drain pipe would have to be insulated so that it would not free in the Winter, but I don't see why it would not work.


What do you think ?

[Jamie Buxton]

That's how mine is installed -- the condensate line just runs to free air. But my area barely gets frost, so freezing isn't an issue. It does dribble water any time the furnace is running, so you probably want to pipe it down to the ground, rather than just letting dribble down the face of the building. Come to think of it, that might be an issue for you. You couldn't keep the whole downspout insulated against freezing.

[Mike Wilkins]

I have seen set-ups like you describe, with the drain pipe routed through the exterior wall. Be sure to put some slope in the line, wrap it to prevent freezing in the winter, and put a screen over the pipe termination to keep the critters out.

But most important, check and ream out the pipe on a regular basis. Blockages from gunk and mildew build-up can clog the line and cause a mess on the interior of your home.

[Lee Schierer]

Where does the flue go? Any chance you can slope it so the condensation will drain? Is there a vent pipe for the sinks or toilets you can get to?

[Randy Red Bemont]

I think just day lighting the drain pipe through the wall is going to be trouble in the winter months. There is not going be much flow of water and the cold is going to stop it in its place. I had a footing drain around my house when I live in CT that had very little flow and in a cold winter it would freeze up solid right at the end of the pipe. Just my two cents worth.

Red

[Clarence Martin]

Where does the flue go? Any chance you can slope it so the condensation will drain? Is there a vent pipe for the sinks or toilets you can get to?

Flue goes straight up through the attic and out the flat roof. Here is the problem: That 2nd floor is not used . It used to be for a 2nd unit apartment, but is not being used. The heat ducts, as I mentioned in a prior posting some time ago about this furnace, were installed a LONG !! time ago , in the attic. The flat roof is so close to the furnace duct work towards the edge of the flat roof that, even with the pipes wrapped, 14 inches of blown in insulation in the attic and ridge vents, I think that is what they are called, the ice still builds up in the Winter. Now, if I set the thermostat between 55 and 60 degrees during the Winter, there is no water leaking out of the bottom of the flu. But, the problem with that, is that the heat builds up in the attic, creating the ice dams, water leaks and icicles. If I turn the furnace down to 45 to 50 degrees, I don't get any ice build up, but I have to go up there every couple of weeks and drain the bucket.

I was told by 2 roofers and 2 furnace men , that the way the duct work is installed, there is no way any amount of venting will get rid of all the heat.

So, that leaves one option, the condensate drain.

[Clint Baxter]

Have you considered a condensate pump? They collect the condensate and then pump it through a tube which you can then route to a suitable drain location. You don't have to worry about slope and can route the drainage to a location higher than where it is being collected. Might be easier than doing the gravity drain. It would typically be routed to a floor drain, laundry sink, or even the drain pipe for a washing machine.

Clint

[Lee Schierer]

If I turn the furnace down to 45 to 50 degrees, I don't get any ice build up, but I have to go up there every couple of weeks and drain the bucket.

I was told by 2 roofers and 2 furnace men , that the way the duct work is installed, there is no way any amount of venting will get rid of all the heat.


From where I set, it appears that you may have been misinformed by your roofers. In order for heat to escape from any vent you have to let air into the space from a lower vent. I'm not sure how you put a "ridge vent" on a flat roof, but if the soffets aren't equipped with vents to let air in the "ridge vents" aren't going to let the heat out. It also sounds like your duct work has leaks that the furnace fan is pushing heated air out of into your attic. I would suggest that you have an HVAC company do a smoke test on your duct system to determine where it is leaking. Most likely it will save you a good amount of heating dollars and may also solve your condensate problem.

[Phil Thien]

Have you considered a condensate pump? They collect the condensate and then pump it through a tube which you can then route to a suitable drain location. You don't have to worry about slope and can route the drainage to a location higher than where it is being collected. Might be easier than doing the gravity drain. It would typically be routed to a floor drain, laundry sink, or even the drain pipe for a washing machine.

Clint

This. If it were me, I'd pump the stuff into the attic and tap into a vent stack (under the insulation, of course).

[Clarence Martin]

From where I set, it appears that you may have been misinformed by your roofers. In order for heat to escape from any vent you have to let air into the space from a lower vent. I'm not sure how you put a "ridge vent" on a flat roof, but if the soffets aren't equipped with vents to let air in the "ridge vents" aren't going to let the heat out. It also sounds like your duct work has leaks that the furnace fan is pushing heated air out of into your attic. I would suggest that you have an HVAC company do a smoke test on your duct system to determine where it is leaking. Most likely it will save you a good amount of heating dollars and may also solve your condensate problem.

I should have said Soffit vent. It's the vent along the edge of the roof near where the gutter on the flat roof used to be. There is 4 regular roof vents on the regular pitched roof on the other part of the house.

[Lee Schierer]

Are the two roof sections connected to each other so that air can easily flow between them? Are the vents in the other roof functional even with several inches of snow on the roof? How large are these other vents?

[Clarence Martin]

1. Yes.

2. yes.

3. Approximate size is 15x17

[Lee Schierer]

3. Approximate size is 15x17

How many vents of that size and what is the total area of the roof?

[Clarence Martin]

How many vents of that size and what is the total area of the roof?

4 Vents

House is 34 x34 Half the house is flat roof, other half is regular pitched roof. If I recall right, it is 18x34.

[Lee Schierer]

It sounds like you have adequate venting if your soffet vents are allowing air in. So, that would indicate your heating duct work has some significant leaks.

[Jim Becker]

The condensate drain for the HVAC system in our addition (attic install) leaves the building at the soffit and dumps into the rain gutter.

[Jason Roehl]

Just a couple of thoughts I had that I haven't seen mentioned:

1. If the drain line is a fairly short run, the condensate should be pretty warm, and not terribly prone to freezing.

2. Be careful how/where you route a drain line, as the condensate can also be quite corrosive as it runs back down the exhaust pipe and picks up combustion by-products.