I am in the process of building a small blacksmith shop and have a important question. I have built a side draft flu out of 3/16 steel 5' long coming out of the back wall. My flu pipe go up outside up to the ridgeline. 12" galvinized culvert pipe is what I want to use, for reasons of longevity and durability. Now I need a few opinions. I am 8' from side draft to peak of roof.I have read a lot of recomendations to get it 4' above roofline. Problem is pipe is $8.34 per foot and comes in only 10 and 20 ft. sections. A 10' section will get me 2' above ridgeline. I don't want to buy 10' to find out it doesn't draw well and I don't want to pay the extra cost and cut 4' off. Whaddya think? 10' work? Thanks Randy.

would not use culvert pipe for a chimney.... you should be able to get stovepipe much cheaper and it will work better ....

Spiroduct is many time stronger than plain stove pipe and costs only a few dollars more.

Sounds like you are buying it new; must you? What are the local wind patterns?

If it doesn't work, how hard would it be to add the extra lenght later?

 

Phil

What danger is there in using a galvanized pipe? It is not directly in the fire but will it get hot enough to be a danger from fume fever?

I don't think wind will be a problem I will brace it real well. Also have not had any luck finding used that is in very good shape. Hadn't thought about adding to it. Don't think it is something I would want to do.

Its been a while but I seem to remember the rule is 2' in 10'. You want to be 2' about anything 10' away. If the ridge is 12' away, you don't need to be  2' above it...

 

As others have said, the culvert seems an unnecessary expense....

The culvert will outlast anything except stainless steel 10:1. It is quite rigid and requires no extra bracing like thin duct. Unless the galvanized metal is in the fire, no problem with outgassing.

 

Other buildings, trees, slopes may affect the wind patterns and the draft from the flue. An easy fix/upgrade to a too short straight uncapped flue is to add a section of larger diameter tube to the top as an overlapping sleeve: it adds height and helps to keep rain out of the firebox.

I was at the local junk yard shopping for odds and ends, when I found lenghts of 8" pipe 10 ft long. I was thinking these would work for culverts in some of my woods roads, so I bought 4 or 5 at scrape price, Wish now I had bought all of them. These were water pipes used to make snow at a ski area, they are heavy walled so you can weld to them without burning thru. Never did use them for culverts, instead used two of them to extend flue pipe on outdoor furnace. Think someone here already hinted you towards scrape yard. I have seen old sign poles from business used for flues, I would check the junk yards and ask them to keep a look out for what you want, just a thought.

                                                  Adirondacker

What do you really save if you have to go back and change the plan? We have all seen culverts used to make chimneys , as well as spiral ducting and other tubing. To not use 12 inch diameter is a mistake..it is a minimum thing, with air and resistance as it moves up the chimney. Maybe in you area there are substitutes.

 

In our area culverts were priced "by the foot" but were only available in certain lengths, regardless of what you wanted. If I went to the trouble of erecting a new chimney I would not want it to not perform as well as possible or have to take it down and add more to it.  Backtracking is not a preferred method of travel (work). Spend good money for good work (tools).

 

 

Carry on

David I totally agree with you. I just hate to buy the extra 10' of pipe only to cut 8' off. I'm going up today and am going to stop at scrap yard to see what they have.Right now I am leaning toward the 10' section which will extend 2' above ridgeline. No firm decision yet. Thanks Randy.