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condensate dilemma

Royboy Member Posts: 223
helped a pal out by completing the install of a Quietside condensing water heater. he had hung it on the wall and I did the rest. its in a slab-on- grade duplex in a little utility closet that is between the two garages (heated) and the door opens to the outside.

one of my last things was to hook up the condensate line and look around for a floor drain. turned out there was none in the utility closet. each garage has a floor drain in the center but he told me they are just plumbed to daylight out 20' in the back yard. I'd be afraid that the constant trickle in our harsh northern WI winter would slowly fill the drain line with ice til it plugged. not to mention that the acidity would not be good for the lawn around the discharge point.

he's willing to discharge through the outside wall but again I'm dubious about freezing up, plus there's a 3' wide concrete apron that has to be crossed to reach dirt (I understand the condensate, unless neutralized, is pretty tough on concrete).

I'm wondering about a bucket of limestone chips for condensate neutralizing, then a condensate pump so that the fluid doesn't just trickle out but discharges a bunch at a time.

anyone recommend a model that comes with good safety switches so that if the discharge line gets blocked (by freezing or otherwise), it will shut things off.

or some other approach???


  • Steve Whitbeck
    Steve Whitbeck Member Posts: 669
    edited August 2010

    I would rather have water on the floor than a heating system that got turned off by a failed condensate pump.

    Can you just drill a 2 inch hole in the floor and see if it will take the condensate without spilling over .

    I did this in my barn and it works great.

    take a piece of 1 1/4 copper and dig a little hole below the 2 inch cut.
  • Royboy
    Royboy Member Posts: 223
    outa the box

    with that approach! which I appreciate.

    the rub there is that there's tubing in the slab, so I'd have to be pretty certain I wasn't going to hit it if drilling through the slab ...

    probably a sand lift under the slab that could handle some condensate ... but clay below that, which would be quite slow to absorb anything.

    might give that some thought though ... and then try to figure out how to be sure to not hit tubes ...
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Would that not cause problems...

    Would not cutting a hole in the floor and dumping condensate there cause problems with the acidity eating up the floor from beneath? Since I am not a contractor, I do not know how much problem this is in practice. I know my contractor had to deal with the condensate problem. My mod|con is in my garage that has a concrete floor and no drain.

    Around here, it is legal to put the condensate into a cast-iron drain. It is not clear to me if it needs to be neutralized according to the code, but in any case the nearest drain is over 20 feet away and further if you consider the path the condensate would have to run (upstairs to second floor, over the ceilings, back down to the PVC from the kitchen sink drain, and out to the sewer system. They would have to rip out some flooring and drywall to run the tubing. Ugh!

    Option 2 would have been to go outside below grade, and through large diameter PVC to a dry well. But there is a problem there in that some inspectors allow that and some do not.

    They opted for option 3: use an adapter to raise the 1/2" diameter flex tube up to 1 1/2" PVC, go through the outside wall and let it dribble on the ground there, and see if the inspector would allow it. (If not, see what he would say about what he would accept, and then do that.) We never found out, because the inspector never looked or asked where that pipe went. Now my house is just 1100 square feet (700 downstairs, 400 upstairs) Cape Cod in New Jersey where it seldom gets very cold (I used to live in Buffalo, NY, where it does get cold). So it does not pump a gallon per hour of condensate all winter long. The acidtiy does not seem to be harming the grass and green plants (periwinkle?) there. I wish they put the pipe higher off the ground though. It is about 18" up, and it snowed enough to cover the end once or twice last winter. This was not enough to block the condensate, but I suppose it could.
  • Jack
    Jack Member Posts: 1,047
    It can absolutely cause a problem...

    But, the "out of sight, out of mind" view prevails at times. Years ago I got a call to look at a job. A homeowner had gotten hold of a condensing appliance I was working with at the time. He installed it for temporary/construction heat. At the end of the winter when I got there his new 4" slab was about 1 1/2" thick in about a 12' circle surrounding the furnace. The one thing he did right was suspend the SA plenum from th12e floor joist, which was a good thing as the bottom 2-3" of the furnace was gone too.

    My point is that if you punch through the floor I would suggest a large enough core drilled hole to be able to run a small well point a few feet into the subsoil to allow the condensate to get below the floor far enough to eliminate the errosion. Going below the floor is kind of a "hit & hope" deal. Kinda like my golf game
  • hot_rod
    hot_rod Member Posts: 22,263
    no other drain nearby, inside?

    what about a washer drain?

    With 1/2" pex you could pipe the condensate line quite a distance. I has to run my softner drain across the shop, up and across the ceiling, when the "soak away" floor drain refused to handle the flow.

    You can buy self regulating heat tape suitable for plastic pipe if you need a last ditch solution, to run outside for a distance.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    What HR said...

    First, and most importantly, NEUTRALIZE.

    Second, set up a submerged 5 gallon bucket as the receiver flush with the mechanical room floor and install a decent submersible pump. DO NOT USE THE CHECK VALVE normally used in this application.

    Third, pipe it to a sanitary drain or plumbing vent in the attic, making certain that where the pipe goes from the vertical to the horizontal, that point is the highest part of the drain pipe, avoid sags or droops and run it to a sewer connected drain.

    Sequence of operation: Appliance produces condensation, is neutralized and directed to the bucket. Condensate builds up to the point that the sub pumps float switch is activated, and fluid is forced up and out to the sanitary sewer. Pump float shuts off pump, and fluid standing in the riser (potential freeze situation) drains back to the bucket. By using a smaller than normal pipe size with a healthy pump, you will avoid the pump short cycling against itself.

    I would protect the horizontal portion in the attic with a self limiting heat tape as HR describes.

    I froze my sanitary sewer up here at 8,000 feet last Fall. I had left my modcon running on low heat, and the continuous production trickle of condensate running through a shallow section of the building drain ended up freezing up to the point that condensate (and OTHER things...) were backing into the floor drain serving the mechanical room. I had to resort to Eatherton ingenuity to get the sewer thawed out, then used the scenario listed above to avoid any further issues for the winter.

    Last Fall was extremely cold, with little to no snow on the ground to act as insulation to keep my building drain from being exposed to extremely cold conditions. I do not believe that is the norm, but has to be covered in any case.

    Proceed with caution. I'm not a big fan of creating LARGE caverns below concrete floors with condensate. I think Dan had a story about a boiler falling through a floor. Not a pretty sight.


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  • Royboy
    Royboy Member Posts: 223
    a couple questions

    Mark -

    I understand why neutralize if discharging into CI or on concrete or via acid-intolerant pump... but if into PVC drain where it will get diluted with other waste-water ... I'm not so sure why neutralizing is needed & most important.

    why do you recommend a regular submersible rather than a condensate pump? is it the greater pump flow rate? the larger size that could avoid short-cycling from drainback from the discharge line when the pump shuts off?
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    Humpin' and a pumpin'....


    If you are not on a septic system, and all drains and mains are plastic, then you needn't neutralize, but not knowing for sure who all would read this post, I thought it best to cover all bases.

    On a septic system, the acidity will kill any working bacteria, and destroy the functionality of the waste elimination system. Hence, importance.

    The reason for recommending a larger sump pump is because they have a longer/deeper throw to their float switches, and they get the job done in a a hurry. You don't want to trickle this stuff in an attic environment with freezing conditions. You want to get 'er done!!


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