Sweating large diameter copper pipe

We are in the middle of renovating a kitchen and bathroom. House was built in 1925, and kitchen pantry was converted to a bathroom I'm guessing in the 1950's. Current plumbing vent for the bathroom is 2" copper run on the exterior wall of the house. This vent will be moved into the wall cavity. (Already have the walls ripped out and holes in top plates drilled.) Hired plumber will be doing most of the work.
I'd like to reuse the current copper vent pipe inside the wall. I have no sound reasons for wanting to reuse the pipe other than I just like the idea of reusing old materials rather than always buying new, even if it adds to the cost of the job. We'll be asking the plumber about this, and I anticipate that his answer will be that it is way easier and cheaper to just run new PVC inside the wall than trying to clean up the pipe enough to sweat new couplings on as sections of the pipe are stuffed up the wall cavity.
Also, current waste pipe for the toilet is 3" (I think) copper. This had to be cut in one place as part of the renovation, so it would only take one coupling to reconnect the existing waste line to the new stuff.
So my question is, how hard is it to sweat a 2"+ diameter copper pipe? I've done plenty of 1/2" and 3/4", so I know how easy it is to do that, but does it become exponentially more difficult to sweat larger diameters? Is the plumber going to run screaming from our house if we ask him to do this? I assume he will want to just rip everything out and re-run PVC, so should we let him do this?
Thanks for any insight anyone can give me.
Ken
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Any real plumber will have a torch that can easily solder 2" copper pipe. The real issues are how accessible it all is, how easy it is to get to the right spots to cut/solder it, and how much harder or costly it will be to do that instead of going with ABS
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On 15 Jun 2005 11:24:48 -0700, snipped-for-privacy@optonline.net wrote:

Around here it is hard to find a plumber who knows anything but "pasting plastic". I think most of them get into the trade because they like the smell of the glue
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With a big "turbo torch" it is done daily. The average plumber may not have such a tool. Never seen one at a rental yard.
Last one I saw the flame end was 4 inches in diameter and they used dual gasses. Oxy and Acetylene. Took a skilled journeyman about 30 minutes a joint. No flammable materials anywhere near.
Since this is for a vent I would think about a "no hub" connection.
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Glad this post is about plumbing because the last answer is as full of shit as any sewer i have ever seen. No turbo torch, no oxy assist feed. Average plumber will have a BTank that will handle job, prob is the labor to clean the couplings off old solder. Average joint only needs a minute to heat.
-- Troweller^nospam^@canada.com
Remove the obvious to reply. Experienced and reliable Concrete Finishing and Synthetic Stucco application in the GTA.

have
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"Glad this post is about plumbing because the last answer is as full of shit as any sewer i have ever seen. No turbo torch, no oxy assist feed. Average plumber will have a BTank that will handle job, prob is the labor to clean the couplings off old solder. Average joint only needs a minute to heat."
I got a good laugh out of it too. Turbo torch with 4 inch diameter flame and 30 mins a joint to solder a 2" copper pipe. LOL He must have been smoking a joint and watching a shuttle launch!
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I brazed 2-5/8"(?) AC lineset for a 50 ton commercial unit with a oxy/acetylene torch. Each joint probably took a couple of minutes. Soft solder would have been faster! Greg
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SQLit wrote:

That had to have been on a government job. Were there 5 or 6 "inspectors" standing around watching and a guy with a fire extinquisher?
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Robert Allison
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If it took 30 minutes a joint, he was far from a skilled anything. Even a hack can to that type of joint in just a couple of minutes.
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Edwin Pawlowski wrote:

Maybe it was standing full of liquid H or something so it was hard to heat! :)
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We have done exactly this quite a few times. I suspect he saw a repair job on large, heavy copper water line. We have used two rosebuds (there is your 4" diameter flame) to get the moisture out of the line. To get the copper up to solder temperature we certainly do use oxy acetylene on 4" heavy wall copper. A B bottle will work, but I think you would be hard pressed with a typical propane torch. The OP is talking about soldering light weight 2" and I agree that soldering dry thinwall pipe is quite doable with a good propane torch.
(top posted for your convenience) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing . . . . DanG (remove the sevens) snipped-for-privacy@7cox.net

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DanG wrote:

....
That was my read of what he must have seen, too....
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When I used to do a lot more heating and AC installs, the boss and I used to work together on solder joints like that. It was a sight to behold. Two bespectacled Mormons, with ball caps, clip on sunglasses, pockets full of pens. Two mapp torches, and two rolls of solder. We'd talk about anything and everything while the pipe heated. Hit it with solder, wipe it off, and get on to the next one. That was the good life. Never ridicule nerds, they are the only ones who can fix your furnace and AC.
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Christopher A. Young
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Thanx for supply of another reason to hate mormons and nerds in the same post.
-- Troweller^nospam^@canada.com
Remove the obvious to reply. Experienced and reliable Concrete Finishing and Synthetic Stucco application in the GTA.

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In a job I once worked on, the (master) plumber had to fish a long run 2" copper _through_ the floor joists. Meaning he had to solder the pipe between each and every joist.
[This was half of a duplex - in "commercial" work, you have to use copper even for DWV. Here at least... He did quite a bit of other large-diameter copper too.]
He was using an acetylene torch without oxygen. A small tank with a hose to the torch.
It didn't take him very long to do 20ish connections.
Not a big deal - to him at least ;-)
You might find it relatively difficult to do yourself with a standard cheapie propane torch, but if you used MAPP/MPS cylinder instead, it should be considerably easier. I use MPS gas myself now, because it's considerably quicker - especially if I have to solder something outdoors in high winds ;-)
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Chris Lewis, Una confibula non set est
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