unscrewing old pipe without threads breaking

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CharlieNH

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I'd like to try unscrewing a section of 1-1/2 inch galvanized pipe from a vent line inside a wall, but not if there is a high risk that it will break off at the threads where it goes into a heavy, probably cast iron, elbow up in the wall, as that would make the reconnection of the new vent plumbing more difficult. These pieces have been together for 55 years. What do you think is the chance that it will unscrew successfully and not break off? I'm look for some people with some experience with this. Can't use any flames to heat the ell.
I can get plenty of force on it to turn it from the basement level. I've already put quite a lot on it with no effect, but I can up the force with essentially no limit.
 
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Cwhyu2

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Cut it off 3" from threads with a sawzall and use a proflex coupling to attach your new pipe.

proflex.jpg
 
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The trouble is that I can't get at it to cut it there, which is what I first hoped to do.

Charlie,
You said earlier that "I can get plenty of force on it to turn it from the basement level. I've already put quite a lot on it with no effect, but I can up the force with essentially no limit."

If you can get a wrench on it that easily, then you should be able to cut it with a long, thin metal cutting blade in a Sawzall, and if it's not a perfectly flat cut, who cares?

Just use the fitting that CW pictured and you're all set.

HE
 

CharlieNH

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pipe access

The pipe goes up about six feet into the wall from the open basement ceiling. To try to turn it I use a long pipe that slides up inside it and pin the two together with a grade 8 bolt. I can just get access with an angle drill to put the hole I need through the pipe, but I can't get a saw in. So the thing I'm really wondering about is what happens to those joints over 50 years and whether the thinner part of the pipe where it's threaded can withstand the torque needed to twist it. On small pipe, the old joints always seem to break rather than twist, which this vent pipe did at it's bottom joint, but that was more exposed to moisture and waste at the bottom where it vented the waste pipe from a toilet. So the top end might not be so deteriorated.
 

Kingsotall

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If it's like anything else in plumbing it'll break off and some other one of Murphy's Laws will rear its ugly head as well. Time to get some professional plumbing help onsite¿
 

NHmaster

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In my experiance, it will either back out fairly easy or it will snap off at the joint. Either way, once it's out you still need to get to the joint to re-install new pipe and fitting. Call a plumber before this small job turns into a major headache.
 

hj

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pipe

IF it has not broken off by now, then it will not even with a larger, or longer, wrench. BUT what could happen, is that the tee itself could shatter if it has weakened with age.
 
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