# Gas Furnace Leaking Water **URL:** \ **Category:** Factual Questions\ **Created:** [December 7, 2012, 4:09am UTC](https://boards.straightdope.com/t/gas-furnace-leaking-water/643272 "2012-12-07T04:09:23Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [December 8, 2012, 3:38am UTC](https://boards.straightdope.com/t/gas-furnace-leaking-water/643272/21 "2012-12-08T03:38:17Z")
> [@dauerbach](#): > > Raindog, I appreciate the information. The guy I hired was recommended by a neighbor. I don’t really know anything more about him, although I am beginning to think that perhaps I should have hired someone else. Was it a ‘guy’ or a company. Sometimes you can hire a good company but still get a bad installer. That’s why I suggested earlier that if it’s an actually company you call them back and talk to a supervisor. It would be good for someone to come out and see his work. If it’s just a guy, you should probably take some pictures of this and consider just getting the correct parts and finishing the installation yourself. Connecting PVC isn’t rocket surgery. Also, as I said earlier, if he pulled a permit, get the city inspector out to take a look at his workmanship. If all he did was stick a 2" pipe into a 2.5" pipe with no reducer, he’s literally pumping exhaust into your house. Again, catching things like this is why you pull permits. It’s an uninterested third party that makes sure people aren’t cutting corners by using duct tape and bathtub caulk instead of PVC and cement. ---
**Author:** ![raindog](https://avatars.discourse-cdn.com/v4/letter/r/2bfe46/32.png) [@raindog](https://boards.straightdope.com/u/raindog)\ **Post date:** [December 8, 2012, 4:37am UTC](https://boards.straightdope.com/t/gas-furnace-leaking-water/643272/22 "2012-12-08T04:37:07Z")
> [@Joey\_P](#): > > Was it a ‘guy’ or a company. Sometimes you can hire a good company but still get a bad installer. That’s why I suggested earlier that if it’s an actually company you call them back and talk to a supervisor. It would be good for someone to come out and see his work. > If it’s just a guy, you should probably take some pictures of this and consider just getting the correct parts and finishing the installation yourself. Connecting PVC isn’t rocket surgery. > Also, as I said earlier, if he pulled a permit, get the city inspector out to take a look at his workmanship. If all he did was stick a 2" pipe into a 2.5" pipe with no reducer, he’s literally pumping exhaust into your house. Again, catching things like this is why you pull permits. It’s an uninterested third party that makes sure people aren’t cutting corners by using duct tape and bathtub caulk instead of PVC and cement. +1 ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [December 10, 2012, 12:49pm UTC](https://boards.straightdope.com/t/gas-furnace-leaking-water/643272/23 "2012-12-10T12:49:58Z")
> [@Joey\_P](#): > > If water is leaking out of the exhaust, so is CO. Not clear to me whether this the case. From the OP: > [@dauerbach](#): > > This water seems to be coming from a 2 inch pvc pipe labeled exhaust. If the pipe is PVC, then this doesn’t sound like the main flue gas exit duct; that should be made of metal, unless different building codes apply to ultra-high-efficiency furnaces _(in which the flue gas is so cool that water condenses out)_. Hopefully **dauerbach** can clarify, but I’m guessing the PVC pipe he refers to is in fact the drain pipe for that condensate, and leads down to the floor drain. With a properly operating flue gas blower, no exhaust gases should be exiting into the home through the condensate drain, even as condensate flows out to the floor drain. If the condensate drain pipe is leaking from a joint, then that joint ought to be sealed properly - and the installer ought to be brought back to the job site to do it. ---
**Author:** ![Joey\_P](https://avatars.discourse-cdn.com/v4/letter/j/919ad9/32.png) [@Joey\_P](https://boards.straightdope.com/u/Joey_P)\ **Post date:** [December 10, 2012, 1:02pm UTC](https://boards.straightdope.com/t/gas-furnace-leaking-water/643272/24 "2012-12-10T13:02:50Z")
> [@Machine\_Elf](#): > > Not clear to me whether this the case. From the OP: > > If the pipe is PVC, then this doesn’t sound like the main flue gas exit duct; that should be made of metal, unless different building codes apply to ultra-high-efficiency furnaces _(in which the flue gas is so cool that water condenses out)_. The pipes are always PVC on [furnaces](http://www.chimneycricket.com/getattachment/c8885d96-da1f-47b7-99d4-776743410d33/Furnace-Cleaning.aspx) with sealed burners. You’ve seen it a million times. Homes with two PVC pipes sticking out of the sides. [One that dives down and one sticking up](http://summitheating.com/blog/wp-content/uploads/2012/04/HighEfficiencyFurnaceVent1.jpg) with smoke/steam coming out. ---
**Author:** ![dauerbach](https://avatars.discourse-cdn.com/v4/letter/d/c2a13f/32.png) [@dauerbach](https://boards.straightdope.com/u/dauerbach)\ **Post date:** [December 10, 2012, 2:50pm UTC](https://boards.straightdope.com/t/gas-furnace-leaking-water/643272/25 "2012-12-10T14:50:45Z")
The small caliber pvc pipe from which condensate is to flow is distinct from this pipe, which is 2 1/ inch pvc. The guy is coming later today to fix it. I know he needs the reducer, and he knows I know, so I am not expecting any problems. So there was an appreciable amount of water dripping from the pipe. It will soon flow back into the furnace. From there it drains into the same pipe that the air conditioner condensate flows in the summer. Is this correct? ---
**Author:** ![raindog](https://avatars.discourse-cdn.com/v4/letter/r/2bfe46/32.png) [@raindog](https://boards.straightdope.com/u/raindog)\ **Post date:** [December 11, 2012, 3:47am UTC](https://boards.straightdope.com/t/gas-furnace-leaking-water/643272/26 "2012-12-11T03:47:54Z")
Yes this is correct. ---
**Author:** ![raindog](https://avatars.discourse-cdn.com/v4/letter/r/2bfe46/32.png) [@raindog](https://boards.straightdope.com/u/raindog)\ **Post date:** [December 11, 2012, 3:53am UTC](https://boards.straightdope.com/t/gas-furnace-leaking-water/643272/27 "2012-12-11T03:53:06Z")
> [@Machine\_Elf](#): > > Not clear to me whether this the case. From the OP: > > If the pipe is PVC, then this doesn’t sound like the main flue gas exit duct; that should be made of metal, unless different building codes apply to ultra-high-efficiency furnaces _(in which the flue gas is so cool that water condenses out)_. Hopefully **dauerbach** can clarify, but I’m guessing the PVC pipe he refers to is in fact the drain pipe for that condensate, and leads down to the floor drain. With a properly operating flue gas blower, no exhaust gases should be exiting into the home through the condensate drain, even as condensate flows out to the floor drain. > > If the condensate drain pipe is leaking from a joint, then that joint ought to be sealed properly - and the installer ought to be brought back to the job site to do it. To add to Joey P’s post, any furnace above 90% efficiency is a condensing furnace, and will have a PVC flue. (and, of course, a condensate drain) Eighty percent furnaces have metal flues and are non-condensing furnaces and therefore will not have a drain. ---
**Author:** ![daz25](https://avatars.discourse-cdn.com/v4/letter/d/dbc845/32.png) [@daz25](https://boards.straightdope.com/u/daz25)\ **Post date:** [May 8, 2013, 1:44pm UTC](https://boards.straightdope.com/t/gas-furnace-leaking-water/643272/28 "2013-05-08T13:44:36Z")
> [@raindog](#): > > To add to Joey P’s post, any furnace above 90% efficiency is a condensing furnace, and will have a PVC flue. (and, of course, a condensate drain) > > Eighty percent furnaces have metal flues and are non-condensing furnaces and therefore will not have a drain. Thanks for the info on this. [Previous page](https://boards.straightdope.com/t/gas-furnace-leaking-water/643272.md?page=1)