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  1. #1

    furnance condensate drain line

    Hello,

    I am trying to get some advice on what is the proper method (code) on where to drain the furnance condensate drain line.

    I had a new 90 percent efficient furnace installed and they just used a flexible clear hose and it is dripping directly on the dirt in the dirt crawl, there are no drain in the crawl for the condensate line to run to although, there has to be a better solution?

    Draining the condensate line directly on the dirt is unacceptable, and I'm sure it does not meet code in many areas.

    What would be the professional solution, tapping in to the sewer with a trap, using a condensate pump?

    Thanks in advance for the solution.

  2. #2
    Join Date
    Aug 2010
    Location
    Seattle Wa.
    Posts
    168
    Yeah thats the standard hacker method of condensate removal. Its pretty standard to run the tubing through the crawl (it has to be insulated in my area) and then into some 3/4 pvc as it exits to the outside, terminating into a french drain is the best way but you can also stub it out above ground level. It should never be drained right into the crawl space.

  3. #3
    If you stub it out oustide, how can you prevent it from freezing?

  4. #4
    Join Date
    Jul 2010
    Location
    georgia
    Posts
    562
    Thats a no no, especially since some furnaces can produce gallons of condensate a day.

    As an outsider, it doesnt look like the condensate issue has been fully addressed. I've seen so many questions about how to plumb it and how to keep it from freezing.

    I'm in an ongoing process (since June) of getting a new 90%+ furnace installed, and after reading many things on condensate, my plan is to get the condensate pump as close as possible to my bathroom, and then I will run the condensate output into the drain for the bathroom sink (you can buy an adapter neck that has the 3/4" fitting on it).

    Although the mfgs say all of the condensate plumbing should be heat tape wrapped if theres a possibility of freezing, heat tape is not supposed to be applied to vinyl tubing (the output of the condensate pump). So either the output needs to be PVC (which can have heat tape applied) or super insulate the nylon tubing. Thats why I'll try to keep that run as short as possible.

    And dont forget an emergency pan in case your condensate system fails.

  5. #5
    Join Date
    Aug 2010
    Location
    Seattle Wa.
    Posts
    168
    Quote Originally Posted by jsmith27 View Post
    If you stub it out oustide, how can you prevent it from freezing?
    I'm speaking in regard to my climate/codes, both the vinyl tubing and the 3/4 pvc have to be insulated in un-conditioned spaces to prevent it from freezing. I use insultube for this and it works great. The vinyl tube tends to freeze up easier so I recommend using 1/2 instead of 3/8.

  6. #6
    Join Date
    Jul 2004
    Location
    Massachusetts
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    6,841
    Quote Originally Posted by heating_seattle View Post
    I'm speaking in regard to my climate/codes, both the vinyl tubing and the 3/4 pvc have to be insulated in un-conditioned spaces to prevent it from freezing. I use insultube for this and it works great. The vinyl tube tends to freeze up easier so I recommend using 1/2 instead of 3/8.
    This cracks me up. Insulation SLOWS the transfer of heat from warmer to cooler when that heat is being transferred by conduction. But insulation has no capacity to create heat and therefore, over a period of time, the tempeature of the product inside the insulation will reach the same temperature as outside the insulation. So if a 90+ condensing gas appliance is drained into an unheated space, either the space stays above 32 to prevent freezing or the condensate freezes during set-backs or other times when there's a long enough dwell between heat calls.

    In fact, unless the crawl is vented with significant vents, it's unlikely it even reaches the freezing point. If the furnace and ducts are all in crawl, then the conduction heat loss through the insulated ducts and the heat rising from the earth is sufficient to keep the core of the crawl from freezing. Insulate if you must but it's a waste of time and material, IMO.

    We also encounter freezing temps in our neighborhood but our concern is for both crawls, basements and attic installs where the condensate will be ejected into sub-freezing temperatures. Again, it's the dwell time in our area that's the issue. So we too use vinyl, non-insulated between the condensate pump and the outdoors. At the terminal point on the side of the house, we secure the tubing indoors so it cannot move. We install the tube so that the final 6-12 inches has a shallow pitch toward the exit. This will allow the last 6-12 inches to vent and drain/drip out of the tubing when the pump shuts off. (In rare instances where we can't assure this, we will remove the check valve from the condensate pump and run the tubing up at leat 4-feet above the pump. This will create a partial vacuum at the pump discharge when the pump turns off and 'suck' the water back toward the pump. Naturally, the pump cycles more but that's not a bad thing if freezing of the drain is a real consideration.

    At the terminal, we make absolutely sure that the end of the vinyl does NOT protrude out into the atmosphere. That is to say, it is absolutely flush with the siding on the house. Leave any vinyl outside, you'll have a freeze. We also remove insulation in the bay where the vinyl tubing exits so that the warmer crawl space air will have better contact with the vinyl tubing for the full extent.

    Using this method for years, we've never had a frozen condensate line. Maybe this wouldn't work where the weather is more severe but it works for us.
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  7. #7
    Join Date
    Aug 2010
    Location
    Seattle Wa.
    Posts
    168
    Quote Originally Posted by skippedover View Post
    This cracks me up. Insulation SLOWS the transfer of heat from warmer to cooler when that heat is being transferred by conduction. But insulation has no capacity to create heat and therefore, over a period of time, the tempeature of the product inside the insulation will reach the same temperature as outside the insulation. So if a 90+ condensing gas appliance is drained into an unheated space, either the space stays above 32 to prevent freezing or the condensate freezes during set-backs or other times when there's a long enough dwell between heat calls.

    In fact, unless the crawl is vented with significant vents, it's unlikely it even reaches the freezing point. If the furnace and ducts are all in crawl, then the conduction heat loss through the insulated ducts and the heat rising from the earth is sufficient to keep the core of the crawl from freezing. Insulate if you must but it's a waste of time and material, IMO.

    We also encounter freezing temps in our neighborhood but our concern is for both crawls, basements and attic installs where the condensate will be ejected into sub-freezing temperatures. Again, it's the dwell time in our area that's the issue. So we too use vinyl, non-insulated between the condensate pump and the outdoors. At the terminal point on the side of the house, we secure the tubing indoors so it cannot move. We install the tube so that the final 6-12 inches has a shallow pitch toward the exit. This will allow the last 6-12 inches to vent and drain/drip out of the tubing when the pump shuts off. (In rare instances where we can't assure this, we will remove the check valve from the condensate pump and run the tubing up at leat 4-feet above the pump. This will create a partial vacuum at the pump discharge when the pump turns off and 'suck' the water back toward the pump. Naturally, the pump cycles more but that's not a bad thing if freezing of the drain is a real consideration.

    At the terminal, we make absolutely sure that the end of the vinyl does NOT protrude out into the atmosphere. That is to say, it is absolutely flush with the siding on the house. Leave any vinyl outside, you'll have a freeze. We also remove insulation in the bay where the vinyl tubing exits so that the warmer crawl space air will have better contact with the vinyl tubing for the full extent.

    Using this method for years, we've never had a frozen condensate line. Maybe this wouldn't work where the weather is more severe but it works for us.


    I dont know the technical aspects of the drain insulation, all I know is that I have fixed a ton of frozen drains by insulating them. There's obviously some merit to it because it works every time. A while back I worked for a big company in my area, at the first cold snap of the year they got about 50 no heat calls that were due to frozen drains. I fixed about 10 of them that week by insulating the pvc and tubing. The tubing that was frozen was always in the garage, some insultube and 30 min fixed them. Never got any calls on them after, why is that?

  8. #8
    Join Date
    Jul 2010
    Location
    georgia
    Posts
    562
    for stagnate water, then yes the insulation effect will "wear off" over time, however in a system thats operating, the condensate coming out of the furnace has heat, and the condensate should also be getting heated by the heat tape applied to the condensate plumbing and pump (which is usually recommended by the mfg). Also, since the condensate isnt pure H2O, it has a different freezing point as well.

    If the condensate system is pitched and plumbed correctly using the siphoning effect (which condensate pump mfs suggest) then there shouldnt be much stagnate water in the run to freeze.

  9. #9
    Join Date
    May 2010
    Location
    West Chester, PA
    Posts
    177
    In the two story condos around mine in PA, the 2nd floor unit's condensate line goes into the utility closet's external wall (believed to have no internal insulation and perhaps at best R-8 on the outside) and then straight down to the first floor where the line MERGES with the first floor unit's condensate line, continues down a few more feet, then goes out through the external wall perhaps 6" above ground level (roughly 1.5" juts out from the vinyl siding). All of that condensate line plumbing appears to be 1" O.D. PVC. Nothing is heat taped. Apparently, this arrangement was good enough for the old systems where just a little bit of moisture from the furnace exhaust would make it into the condensate lines. Asking around I've only heard of one problem, involving a cold stretch and a 2nd floor condo equipped with a humidifier. Supposedly, enough ice formed around the drain line that it became closed and then the water backed up and overflowed into the lower condo's closet. Bummed me out because I really wanted to put a humidifier on my system. Anyway...

    I've seen heat tape included in some estimates but when the work was complete there was no heat tape we could locate.

    Perhaps if the drain doesn't trickle water and form a stalactite such a setup can make it through the winter without freezing shut?

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