I recently bought a 3story townhouse that is built on a slab so there is a condensate pump which pumps water up and out somewhere. I am not certain where it goes, but I see a black 1in PVC pipe that comes out horizontally about an inch and the takes a 90 degree bend downward about a foot. I assume it goes out here. I installed a furnace humidifier and ran the drain line into the condensate pump. It has been working fine for a few months until yesterday when I noted some puddles of water on the ground near the furnace. I noticed that the codenstate pump was overflowing. The pump is working fine but there is a blockage in the line.

I tried blowing air into the 3/8" OD tubing up to about 40PSI and it was still blocked. I'm not sure what else I can try. Today happens to be the coldest day of the year around here (20deg F) so I suspect the line may be frozen.

I can see the line being run up into the ceiling along the furnace duct. After that, it is in the drywall ceiling so I cannot see. I assume it then runs straight across (hopefully with a declining angle) to the exterior wall where I saw that black pipe and then down. I do not go to the first floor very often so it is usually around 55deg F, the room above, gets fairly cold, maybe 65degF. The walls should have insulation in them so it is hard to believe it is freezing. I do not know how the tubing goes into the black PVC pipe or if it goes there at all, but if it is getting frozen, it must be around the outlet.

I'm not sure what to do about this. If it is really frozen, I can of course wait until a warm day and test, but I'm not sure how I can prevent this from happening again short of digging into my drywall (or turning off the humidifier).

It would be best to reroute the line completely this way you will know exactly where it is going and take the necessary steps to prevent freezing in the future.

Many HVAC companys use heat special tapes and insulation to prevent the line from freezing since many units are located in an attic space or other low temp areas.

If you are handy you can do the work yourself. Good luck with your project.

I would love to do that but the ceiling is finished with dry wall and I'd rather not have to cut up the ceiling searching for a tubing and then have to go back, patch it up, etc.

But I can't think of any other way to prevent this problem.

I still find it a little hard to believe it is freezing in the ceiling or wall since there is insulation there and the rooms are 55deg or up

You will never know exactly what is going on since it is covered. Sorry but there is nothing much I can do from here.

Thanks for the help. The furnace is in the garage, so I think I will try running another line out the front of my garage. At least that way I can see it.

Sounds like a plan but do not put it on the driveway. Then the driveway will turn to ice. LOL

Haha, I plan to drill a hole in the wall next to the garage door and let it drain in the dirt next to the driveway. What's the best way to go through the exterior wall. I had planned to use the 3/8" OD tubing from the pump going up to the ceiling, then run it down the length of the garage (with a downward slope), and then drop it down to where I plan to put the hole. Then I figure I'll get some 1" PVC piping and drip the tubing loose into there. As for the PVC piping, I figure I'll have it vertical for where the tubing drops in, then do a 90 degree turn for it to go through the wall, then another 90deg turn downward outside. I'm not sure what to do to seal around the hole. Caulking perhaps