# Exterior Flue Exposed Length **URL:** \ **Category:** Misc. Discussion\ **Created:** [April 1, 2022, 7:33pm UTC](https://forum.nachi.org/t/exterior-flue-exposed-length/213855 "2022-04-01T19:33:26Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![chall20](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/chall20/32/180613_2.png) [@chall20](https://forum.nachi.org/u/chall20)\ **Post date:** [April 1, 2022, 7:33pm UTC](https://forum.nachi.org/t/exterior-flue-exposed-length/213855/1 "2022-04-01T19:33:26Z")
Are exterior flues like this allowed? It is above the roof by 2 feet it appears. I’ve been told this can prevent proper drafting. We do have cold winters here. This was water heater, furnace flue was same opposite side. Processing: 20220401\_093114.jpg… ![20220401_093114](https://global.discourse-cdn.com/internachi/original/3X/c/4/c405887efa49f5a8b21c59dcc43eef75a629dc5b.jpeg) ---
**Author:** ![srechkin](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/srechkin/32/180448_2.png) [@srechkin](https://forum.nachi.org/u/srechkin)\ **Post date:** [April 1, 2022, 8:16pm UTC](https://forum.nachi.org/t/exterior-flue-exposed-length/213855/2 "2022-04-01T20:16:32Z")
The b-vent (assuming it’s what they used) should be enclosed in a chase to protect it against the cold. There is a concern about poor draft and condensation forming with what you have in the picture, especially with a typical low BTU (30-45k) residential water heater. I would double check with local building department if they approve of such installations in your area. The only metal vent I’m okay with on the outside in a cold climate is L vent that receives much higher flue gasses or that of a solid fuel appliance (class A vent). ---
**Author:** ![chall20](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/chall20/32/180613_2.png) [@chall20](https://forum.nachi.org/u/chall20)\ **Post date:** [April 1, 2022, 8:21pm UTC](https://forum.nachi.org/t/exterior-flue-exposed-length/213855/3 "2022-04-01T20:21:27Z")
This one I couldn’t see any labeling on but the furnace was a type B vent on the other side the same way. The strapping seemed good and both were 2 feet above the roof. I see this fairly often so it may be allowed but I thought that poor drafting was a possibility. ---
**Author:** ![jfrederick](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/jfrederick/32/58314_2.png) [@jfrederick](https://forum.nachi.org/u/jfrederick)\ **Post date:** [April 1, 2022, 8:40pm UTC](https://forum.nachi.org/t/exterior-flue-exposed-length/213855/4 "2022-04-01T20:40:03Z")
You didn’t see any issues with/at the water heater as a result of this? What size was the vent piping and the water heater? Yes, it’s allowed when sized and installed properly. That’s a really long run for one appliance. I seriously doubt a water heater could keep that piping warm enough for an effective draft. ---
**Author:** ![chall20](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/chall20/32/180613_2.png) [@chall20](https://forum.nachi.org/u/chall20)\ **Post date:** [April 1, 2022, 8:41pm UTC](https://forum.nachi.org/t/exterior-flue-exposed-length/213855/5 "2022-04-01T20:41:50Z")
I’m not sure I didn’t measure it but the water heater was new and no issues visible. ---
**Author:** ![jmckee](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/jmckee/32/211009_2.png) [@jmckee](https://forum.nachi.org/u/jmckee)\ **Post date:** [April 1, 2022, 10:04pm UTC](https://forum.nachi.org/t/exterior-flue-exposed-length/213855/6 "2022-04-01T22:04:53Z")
where are You located, ? ---
**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:** [April 1, 2022, 10:20pm UTC](https://forum.nachi.org/t/exterior-flue-exposed-length/213855/7 "2022-04-01T22:20:58Z")
> [@chall20](#): > > the water heater was new and no issues visible. Probably recently replaced because the old one was visually suffering from draft problems 😉 ---
**Author:** ![jfrederick](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/jfrederick/32/58314_2.png) [@jfrederick](https://forum.nachi.org/u/jfrederick)\ **Post date:** [April 2, 2022, 10:56am UTC](https://forum.nachi.org/t/exterior-flue-exposed-length/213855/8 "2022-04-02T10:56:52Z")
> [@bcawhern1](#): > > Probably recently replaced because the old one was visually suffering from draft problems 😉 That’s exactly what I was thinking as well ---
**Author:** ![chall20](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/chall20/32/180613_2.png) [@chall20](https://forum.nachi.org/u/chall20)\ **Post date:** [April 2, 2022, 12:47pm UTC](https://forum.nachi.org/t/exterior-flue-exposed-length/213855/9 "2022-04-02T12:47:11Z")
West Virginia Kentucky-Ohio tri state ---
**Author:** ![chall20](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/chall20/32/180613_2.png) [@chall20](https://forum.nachi.org/u/chall20)\ **Post date:** [April 2, 2022, 12:48pm UTC](https://forum.nachi.org/t/exterior-flue-exposed-length/213855/10 "2022-04-02T12:48:35Z")
Unfortunately that’s a very real possibility. Furnace was a few years old with orange flame