# Furnace Pipe What's It Purpose **URL:** \ **Category:** Misc. Discussion\ **Created:** [September 19, 2021, 1:25am UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805 "2021-09-19T01:25:23Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![melyussif](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/melyussif/32/182290_2.png) [@melyussif](https://forum.nachi.org/u/melyussif)\ **Post date:** [September 19, 2021, 1:25am UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/1 "2021-09-19T01:25:23Z")
Can someone tell me what this pipe is for. ![IMG_8568](https://global.discourse-cdn.com/internachi/original/3X/c/5/c5008a6ccf209be1dba083ca0f8fc7efea4b745d.jpeg) The pipe I’m pointing at. Goodman 2006. ---
**Author:** ![ryoung7](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/ryoung7/32/188798_2.png) [@ryoung7](https://forum.nachi.org/u/ryoung7)\ **Post date:** [September 19, 2021, 1:50am UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/2 "2021-09-19T01:50:40Z")
Referred to as a high efficiency condensing furnace flue pipe, Mike. Likely the fresh combustion air intake with the combustion exhaust pipe being on the right hand side. Leaking condensate. Look at the cabinet corrosion. No air break or cleanout for the evaporator. You have the model number? ---
**Author:** ![rmckay](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/rmckay/32/335675_2.png) [@rmckay](https://forum.nachi.org/u/rmckay)\ **Post date:** [September 19, 2021, 2:11am UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/3 "2021-09-19T02:11:57Z")
100% agree with Robert ---
**Author:** ![bnesbitt](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/bnesbitt/32/56701_2.png) [@bnesbitt](https://forum.nachi.org/u/bnesbitt)\ **Post date:** [September 19, 2021, 2:12am UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/4 "2021-09-19T02:12:34Z")
> [@melyussif](#): > > Can someone tell me what this pipe is for. As Robert said likely the fresh air intake. In my area that needs a 1/4" screen to prevent vermin entry. Run the furnace, and see if air is sucking in. Note the rust also. What’s the exact model number? Photo of the nameplate? ---
**Author:** ![ruecker](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/ruecker/32/357170_2.png) [@ruecker](https://forum.nachi.org/u/ruecker)\ **Post date:** [September 19, 2021, 2:28am UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/5 "2021-09-19T02:28:30Z")
> [@melyussif](#): > > Can someone tell me what this pipe is for. Another note on an installation like this. It is not considered a direct vent appliance and the clearances for the exhaust termination change. ---
**Author:** ![ccurrins](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/ccurrins/32/225758_2.png) [@ccurrins](https://forum.nachi.org/u/ccurrins)\ **Post date:** [September 19, 2021, 2:45am UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/6 "2021-09-19T02:45:07Z")
When you remove the furnace cabinet door you will be able to see what it is for. Which is combustion air. ---
**Author:** ![melyussif](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/melyussif/32/182290_2.png) [@melyussif](https://forum.nachi.org/u/melyussif)\ **Post date:** [September 19, 2021, 3:27am UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/7 "2021-09-19T03:27:38Z")
![IMG_8573](https://global.discourse-cdn.com/internachi/original/3X/f/8/f8d81019fac19c8d433bc94d465e65a8f7bb9e20.jpeg) ---
**Author:** ![melyussif](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/melyussif/32/182290_2.png) [@melyussif](https://forum.nachi.org/u/melyussif)\ **Post date:** [September 19, 2021, 3:33am UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/8 "2021-09-19T03:33:13Z")
![IMG_8570](https://global.discourse-cdn.com/internachi/original/3X/e/7/e7ba732eaac8f2df73bd96f6509c8f1cb2454192.jpeg) ![IMG_8571](https://global.discourse-cdn.com/internachi/original/3X/1/b/1bad5c2079c14bc92e63e63a57916c00dc20106c.jpeg) ---
**Author:** ![bnesbitt](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/bnesbitt/32/56701_2.png) [@bnesbitt](https://forum.nachi.org/u/bnesbitt)\ **Post date:** [September 19, 2021, 3:50am UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/9 "2021-09-19T03:50:13Z")
In my area, there’s a requirement that the service manual for the equipment be left with the equipment (thus it’s a defect if that’s missing). [SS-GKS9.indd (acdirect.com)](https://www.acdirect.com/media/catalog/files/goodman_GKS9.pdf) The Goodman® GKS9 92.1% AFUE Single-Stage, Multi-Speed Upflow Gas Furnace features a patented aluminized-steel tubular heat exchanger and energy-efficient Hot Surface Ignition system. * * * The rust appears to not be from the furnace condensate, which is lower down per the manual. Maybe it is from an A/C unit mounted on top of the furnace? Or from the vent pipe? * * * Note from the manual: _For bottom return: Failure to unfold flanges may reduce airflow by up to 18%. This could result in performance and noise issues_ ---
**Author:** ![ryoung7](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/ryoung7/32/188798_2.png) [@ryoung7](https://forum.nachi.org/u/ryoung7)\ **Post date:** [September 19, 2021, 4:35am UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/10 "2021-09-19T04:35:27Z")
Thanks, Mike. Goodman GKS90 - 90,000 BTU - Gas-Fired Furnace - NG - 92.1% AFUE - Single-Stage - Upflow - Multi-Speed. Vintage equipment. Product discontinued. Replacement recommendation: GMSS921004CN. Age: Age: Approximately 15 years old. Probability of failure. Medium. Recommend a licensed HVAC contractor: 1: service the furnace prior the next heating cycle. Looks like a scorch mark on the under side of the exhaust flue. ---
**Author:** ![bcawhern1](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/bcawhern1/32/408713_2.png) [@bcawhern1](https://forum.nachi.org/u/bcawhern1)\ **Post date:** [September 19, 2021, 5:40pm UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/11 "2021-09-19T17:40:26Z")
> [@bnesbitt](#): > > The rust appears to not be from the furnace condensate, which is lower down per the manual. Maybe it is from an A/C unit mounted on top of the furnace? Or from the vent pipe? These things leak like crazy when not serviced. Where and what is leaking is sometimes difficult to pin down. I am curious if this should be connected. I wish had time to look it up, maybe the OP has the opportunity. ![image](https://global.discourse-cdn.com/internachi/original/3X/6/1/619578c6b0a958ac60b0a3005a79d9228a939a8b.jpeg) ---
**Author:** ![eluke](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/eluke/32/177534_2.png) [@eluke](https://forum.nachi.org/u/eluke)\ **Post date:** [September 19, 2021, 8:38pm UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/12 "2021-09-19T20:38:35Z")
I suggest you take some HVAC courses so you can better explain what you are inspecting for you clients. IMO. ---
**Author:** ![melyussif](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/melyussif/32/182290_2.png) [@melyussif](https://forum.nachi.org/u/melyussif)\ **Post date:** [September 19, 2021, 10:50pm UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/13 "2021-09-19T22:50:14Z")
Edward, with all due respect, you should practice some manners and not come off condescending. Not all inspectors need to know everything to be a good inspector. ---
**Author:** ![bnesbitt](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/bnesbitt/32/56701_2.png) [@bnesbitt](https://forum.nachi.org/u/bnesbitt)\ **Post date:** [September 19, 2021, 10:52pm UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/14 "2021-09-19T22:52:40Z")
[quote=“bcawhern1, post:11, topic:203805”] I am curious if this should be connected. [/quote] Sure looks like it should be go somewhere… maybe the black pipe slips over the black nipple? ---
**Author:** ![tglaze](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/tglaze/32/362210_2.png) [@tglaze](https://forum.nachi.org/u/tglaze)\ **Post date:** [September 19, 2021, 10:57pm UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/15 "2021-09-19T22:57:13Z")
> [@melyussif](#): > > Edward, with all due respect, you should practice some manners and not come off condescending. Not all inspectors need to know everything to be a good inspector. Correct Mike! We all have questions everyday on things we may not come across often. There are no and I mean NO boilers in my region, so if by chance I did see one, I would be on here in a heart beat asking questions. ---
**Author:** ![eluke](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/eluke/32/177534_2.png) [@eluke](https://forum.nachi.org/u/eluke)\ **Post date:** [September 19, 2021, 11:05pm UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/16 "2021-09-19T23:05:47Z")
I apologize if I came off judgmental, the intake vent is pretty common on all HVAC units of these age of units. I learn something new on every inspection, and CE study. ---
**Author:** ![melyussif](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/melyussif/32/182290_2.png) [@melyussif](https://forum.nachi.org/u/melyussif)\ **Post date:** [September 19, 2021, 11:24pm UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/17 "2021-09-19T23:24:45Z")
Thanks Edward, it’s all good. I always thought the intake and exhaust always came from outside. ---
**Author:** ![eluke](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/eluke/32/177534_2.png) [@eluke](https://forum.nachi.org/u/eluke)\ **Post date:** [September 19, 2021, 11:40pm UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/18 "2021-09-19T23:40:43Z")
Ya I would guess about 90% of the high efficiency units are vented to the exterior that I see around my area. My own one is not, it terminates in the lower level like the picture you showed. When I asked the HVAC guy who installed it about it, he said being my area is wide open he was not worried about combustion air sufficiently. Also he said that way we didn’t have to cut another hole in the rim joist to the exterior. ---
**Author:** ![dbowers](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/dbowers/32/59651_2.png) [@dbowers](https://forum.nachi.org/u/dbowers)\ **Post date:** [September 20, 2021, 2:51am UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/19 "2021-09-20T02:51:46Z")
#1 - It gets his combustion air from inside the house, SO you need to verify the room its in is large enough to provide that OR it needs a source of the proper CA. If there is NO other gas fired appliance in the room, ALL by itself the furnace needs to have at least 4,500 cubic feet of CA or its a confined space (for example a room 20’ x 20’ x 8’ high ONLY provides 3,200cf of combustion air). #2 - Its been leaking from several places whether it is right now or not. #3 - You’re obviously not really experienced with 90% furnaces, etc … SO #4 - Do the clients and yourself a big favor AND recommend a FULL service checkup PRIOR to close by a licensed and competent heating contractor to VERIFY proper operation and condition, etc #5 - Take more training courses on heating ---
**Author:** ![mmasengale](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/mmasengale/32/176219_2.png) [@mmasengale](https://forum.nachi.org/u/mmasengale)\ **Post date:** [September 20, 2021, 1:26pm UTC](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805/20 "2021-09-20T13:26:36Z")
Yes. That’s the condensate drain from the system exhaust. Prevents water from entering the draft inducer fan, which can be (at least) damaging to the inducer fan or motor, and (at most) make the system inoperable, or (at very most) kill somebody. The hose (now disconnected) channels the condensate to the primary drain. Hence the rusting of the inner casing. [Next page](https://forum.nachi.org/t/furnace-pipe-whats-it-purpose/203805.md?page=2)