My furnace PVC vent pipe is leaking water - WTF ? ! !

[amboy49]

I have a single story ranch and a 90% high efficiency natural gas furnace that’s been in my house for 10 years. Yesterday my wife noticed water dripping from the jointed PVC vent pipe that is used to exhaust the gases through the roof. We’ve not noticed this phenomenon ever happening before. I’m not inclined to crawl up on my roof since it’s covered with snow and ice and at age 68 I don’t bounce as well as I used to - but the shingles on our roof are only two years old so I don’t suspect a leak. Besides, the water certainly seems to be coming from inside the pipe and out at the joint, not down the outside. The furnace is located in our laundry room which is in the interior of the house. The one change that has occurred at our house is that I had several inches of insulation blown into our attic about two weeks ago. I can’t make a connection between the insulation and the leak - but I also don’t have the slightest idea what can be causing this issue.

Any suggestions on what to consider as a cause and a possible fix would be greatly appreciated.

Thanks in advance.

 

[femurphy77]

I'd guess condensation with the temp extremes we've been experiencing. I'm also guessing that there is a code requirement to assure a downward slope for drainage. But HEY; I'm only an electrician, what do I know?

 

[snapping turtle]

First step: A five gallon bucket to catch the water. The same ruined my attic door a few years ago. My brother in law fixed it I would have to ask him what was up.

 

[ChristianPatriot]

The 90% furnaces use PVC flues because the flue exhaust gases can condense inside the pipe. The piping is supposed to slope back to the furnace. There is a series of traps and drains inside the furnace to remove the water. Sometimes you can get away with just running more glue around the outside of the joint. If that doesn’t work, the joint will have to be cut out, replaced, and glued correctly.

 

[edporch]

We had this happen too.
Go through the entire length of PVC pipe and make sure if there's any horizontal runs, that they angle slightly back so the water drains back towards the furnace and doesn't pool anywhere.

 

[tmschuller]

Do you hear water slushing around inside the furnace?? Check your drain. If the exhaust can’t get out it should be shutting down the furnace and showing a code. Doesn’t sound like it’s doing that. Could be the joint there didn’t get glued well enough and it’s leaking. When they blew insulation in they could have bump it?? Just needs cut out and you can use rubber couplers to repair it

 

[amboy49]

From answers so far it would seem the joint has let go. We do have a small pail on the floor for the time being. I did try spraying some flex seal on the joint - but because I have to spray up to the leaking joint the flex seal can’t set up before being washed away. I thought about getting some of the brush on kind to see if I could get it sealed.

The piping does slope back to the furnace at a 45* angle and the furnace has been operating okay (fingers crossed).

 

[lrdudley]

I had the same problem on a new install. I replaced the coupling, but was advised to use the waterproof (blue) PVC cement. I was told that if any moisture is present the regular cement will not make a good seal. Leak free for over a year.

 

[ghitch75]

always use cleaner with the glue on flue pipes......the water has a little acid in it and if you don't use cleaner to weld the pipe it will leak......

 

[Brandon]

Have been on a few calls to either fix or replace pvc flues that start to leak water. Some much older than others. Id cut out the coupler and replace it.

 

[churchmouse]

From answers so far it would seem the joint has let go. We do have a small pail on the floor for the time being. I did try spraying some flex seal on the joint - but because I have to spray up to the leaking joint the flex seal can’t set up before being washed away. I thought about getting some of the brush on kind to see if I could get it sealed.

The piping does slope back to the furnace at a 45* angle and the furnace has been operating okay (fingers crossed).

The joint has to be dry before any repairs can be made on it. Don't use the "Cheap" fixes.
Sometimes you can pull the fitting back a bit and get some glue on the pipe and reset the fitting. Now that you have gooed up the pipe you might have to cut that section out and re-fit it.

 

[Brandon]

May add if you do fix this yourself, please turn off the furnace either on the side of the furnace or at the breaker box.. if those 2 aren't an easy option, take the doors off so the safety switch kills it.

I don't want to hear about something bad in the news.