DIY Chatroom Home Improvement Forum

DIY Chatroom Home Improvement Forum (
-   HVAC (
-   -   Furnace Vent Leaking Water (

Reilley 10-03-2008 09:25 PM

Furnace Vent Leaking Water
My furnace is vented with ABS Schedule 40 (manual states either ABS Schedule 40 or PVC Schedule 40 may be used). It is leaking condensation at a couple of, what appear to be, poorly glued joints.

I've searched a couple sites, HD, Lowes, Google, and can't seem to find any ABS Schedule 40. Does this stuff exist anymore? Am I going to have to replace this entire vent line with PVC Schedule 40? Can I replace the bad section with PVC Schedule 40 and join to the ABS Schedule 40?

I really don't want to spend the money on an entire run of PVC Schedule 40 as it's a good 20 feet. However I'm afraid to turn on the furnace now. Any advice would be appreciated. Thanks.

hvaclover 10-03-2008 11:44 PM

If you can't find ABS run PVC. It's not that hard. My son was twelve and he would run 200 ft of 3" with all the elbows.

Reilley 10-04-2008 12:02 AM


Originally Posted by hvaclover (Post 168095)
If you can't find ABS run PVC. It's not that hard. My son was twelve and he would run 200 ft of 3" with all the elbows.

Use regular glue? Two parts for PVC - primer and glue right?

I've checked lowes and the prices seem cheaper than I originally expected. If I could tie into the rest of the run (20' or so of SCH40 ABS) it would be ideal.

What sould I use to connect PVC to ABS? Currently there appears to be silicon on the outside of the joint, currently occuring between the condensate accumulator and vent stack.

hvaclover 10-04-2008 12:10 AM

Don't know but a plumber's sleeve the same size as existing ABS might work.

Check a regular plumbing store to see if they make a an ABS to PVC adapter.'s sleeve.

8 Ball 10-04-2008 06:08 AM

Fernco coupling. Not allowed on a vent connection.

Marvin Gardens 10-04-2008 08:33 AM

Try adding some more glue around the bad joints after it has been given time to dry out. Sometimes this will work. Force the glue in with a small brush. This type of glue will loosen the previous glue and when the solvent evaporates it just might make a seal. It's worth a try.

Get a carbon monoxide detector and put it on the same level of the house as the furnace. I seriously doubt that you are getting any CO and it is just the condensation from your high efficiency furnace running back to the pump.

If the install was a short time ago call the contractor. He should fix this. If it is a new house call the builder.

If you can't find the ABS schedule 40 go online and order some there. All you need is a short piece with some couplers.

hvaclover 10-04-2008 09:28 AM


Originally Posted by 8 Ball (Post 168127)
Fernco coupling. Not allowed on a vent connection.

They come with every 90% furnace I install. I'm in Mi too so we have the same code.
Have never been knocked down for using them.

Care to eleborate?

SD515 10-04-2008 11:20 AM

My 2 cents:

Gluing ABS to PVC can be done, but it also can be a PITA at times. Proper gluing of PVC requires primer and glue, with ABS primer is not used, PVC to ABS requires a glue design for that use.

As mentioned, a rubber coupler comes with many 90% furnaces in their parts bag for connecting the vent to the furnace. As much as I love the idea of using one downstream in the vent piping, I would have to advise against it, unless you can find one that is listed (UL) for such use. Running drain water through it is not the same as using it in a furnace vent system. True that the likelihood of any problems developing are usually not that great, the use of an unlisted product in such a situation is a gamble with the lives of people at stake. Some of the codes that are written can make one scratch their heads and question why. I understand that. I don't always understand the reasoning behind some of them, but the code is written for a purpose, and it's always better to error on the side of safety then to just 'wing it'.

Some manufacturers allow the use of ABS for the vent system of their furnaces. Personally, I don't like it, and I know that most of that is just me. In reference to the OP's situation, I would replace the vent system with PVC. The price involved to replace a 20 foot run, pipe, elbows, couplers, silicone (for sealing the wall penetration) etc. is minute. But that's just me, and my 2 cents.

hvaclover 10-04-2008 03:30 PM

Don't know about not being listed for the use. But the furnaces I install say to put a field provided plumbers sleeve any where it is convenient in the exhaust or combustion air lines to clear any blockages that may occur.

The material it self is made to with stand the acidic qualities of the furnace condensate.

And if we really want to get picky, PVC is not "Listed" specifically as usable for a condensing furnace. The instruction mandates that only schd 40 and not Thin Wall be used.

Reilley 10-04-2008 08:19 PM

Ok I am replacing the entire run with SCH40 PVC tomorrow. There is a neoprene coupler with stainless clamps between the furnace output (steel) and the condensate resovoire / vent stack (PVC). I'd like to replace it as well. I'm going to pick up another 2" neoprene coupler from the hardware store unless someone can recommend a better option. The furnace manual lists it as Heil part #612689 - Neoprene Nipple 2" x 2" Lg.

I've considered the option of replacing part of the vent line and tying into the rest. The condition of the poorly-glued joints has lead me to replacing the entire run as the rest of the joints probably aren't much better. If I'm going to do it, I'll do it right. After all, I'm dealing with CO here. I like to sleep soundly, but not too "soundly" if you catch my drift.

hvaclover 10-04-2008 08:38 PM

Now you're talking!

8 Ball 10-05-2008 07:42 AM

On the combustion air side, no problem. When the manufacturer provides it, no problem.

What furnace manufacturer are you installing? Most inspectors defer to the manufacturers recomendations, so if it is in the instalation instuctions, no problem.

One of my guys did use one on tough connection point last year and it got hit by the state inspector. response.

All times are GMT -5. The time now is 02:10 PM.

vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
User Alert System provided by Advanced User Tagging (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.

Search Engine Friendly URLs by vBSEO 3.6.1