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I'm trying to disconnect stainless steel drain pipe where it connects to my threaded galvanized pipe so that I can repipe a ptrap for a vanity from the threaded galvinized using pvc.

I'm stuck because I can't seem to pull the steel pipe that is inserted out, despite having loosened what I think is the connection (compression fitting?). I've tried using pliers but I seem to just be deforming the end of the pipe.

Additionally, there's a (brass?) adapter on the threaded galvanized pipe but I can't get it to loosen, despite hitting it with WD40. I'm trying with a plumbers wrench with a rag between the fitting and the jaws.

I'm wondering what other ideas folks might have, or if I'm going about this wrong. (I'm not certain any of my terminology here is correct btw).

My next idea may be to take a grinder a cut the whole thing off, hopefully saving enough threads for a pvc connection. Failing that, my last resort is to open up the wall behind, and cut the section of pipe out from there and in the crawlspace, and then repipe using fernco's to connect to the galvanized.

Below are two photos and my artistic rendering of the situation. I don't know how far the stainless steel pipe is inserted, but it seems further than my finger since I can't feel the end of it.

artistic rendering

side view

enter image description here

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    Have you tried heating it? Bear in mind that the remains of the WD40 may catch fire. Commented Apr 25 at 19:08
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    Good point, I might give that a try first. Nervous about a torch now with the wd40, but maybe a hair dryer might give me a chance and has no open flame
    – Chris T
    Commented Apr 25 at 20:50
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    Hair dryer and a couple of hammer taps and I got the steel pipe out!
    – Chris T
    Commented Apr 25 at 20:58
  • I can write "try heating it" as an answer for you, or (probably better) you can write your own answer about what worked. You can then accept your own answer, but I'm not sure if you have to wait some hours/days before it lets you click the grey tick. Commented Apr 25 at 21:17

3 Answers 3

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Brass is a lot softer than galvanized. Use that to your advantage. By hand with a hacksaw cut the brass adapter in one or two places, being careful not to damage the threads on the pipe. Once cut, use a hammer and cold chisel (or old screwdriver) to dislodge it from the pipe. Hopefully you can then clean up the threads and re-use the pipe without going into the wall.

I wouldn't put more energy into unscrewing corroded parts. Whenever I have done that ... using bigger wrenches, better lubricants, more creativity .... I always end up wishing I went for the saw in the first place. Two minutes and done, just be careful.

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  • Hand cutting is better if one piece is wanted/needed to be reused. Most metal gets quite weak holding together without cutting right though.
    – crip659
    Commented Apr 25 at 19:26
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    After cutting most of the way through the brass above the screw threads (and fully on the rest of the brass ring), insert a flat-bladed screwdriver into the cut and twist. It should fracture and come off.
    – nigel222
    Commented Apr 26 at 9:09
  • Cutting off the front part of the brass adapter first will offer a better view and make it easier to cut the slots.
    – jpa
    Commented Apr 26 at 12:28
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You don't need that pipe fully out. What you need is the brass fitting off.

WD40 is practically useless for this. I would try acetone or some industrial adhesive remover - wear gloves be safe. I would try adding something like that a couple times and some taps with a hammer. And probably removed with monkey wrench.

The metal pipe is so thin and was probably so thoroughly glued it is fused in there. Once you get the brass ring "off" you can cut the cap for the metal pipe.

I would then cut off the rest of the steel pipe and install something like this (https://riverbankbuildingsupply.com/products/cpvc-female-pipe-thread-adapter-with-rubber-gasket-0-5-in) - note I don't know what size you need.

I would not go to a purely rubber connector because of the depth of the threads unless you want to cut them off and open wall. (and like your other answer says, this is an option) I am just not a fan of clamps on purely horizontal - where I use them all the time for main stack drops.

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  • Can you help me understand what you mean by "cut the cap for the metal pipe"? (size of the steel pipe is 1.5")
    – Chris T
    Commented Apr 25 at 20:47
  • @user3213456 - the metal cap/ring would prevent the brass fixture from sliding off.
    – DMoore
    Commented Apr 25 at 20:49
  • Okay, so I got the pipe fully out after a couple of hammer taps. Does that change our plan at all, or should I proceed with cutting the the brass fitting off?
    – Chris T
    Commented Apr 25 at 20:59
  • You can't loosen the brass fitting at all? Heat? Solvents? It would be much easier to just remove it and replace with something like I have in the answer. Another option if the slope is down is just to stick another pipe in there to replace the one you just removed. This would be my second option.
    – DMoore
    Commented Apr 26 at 3:54
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Copious penetrating oil- not WD40- on the galvanised pipe threads. Leave overnight, then see if you can unscrew the brass fitting: use heat if necessary but beware of residual flammables.

If you can't unscrew it then cut it carefully: hacksaw and possibly Dremel to get down into the thread. Clean up any thread damage.

Collapse the stainless pipe with strong pliers and pull it out. The yellow smear looks like some sort of sealant- possibly latex based- which might make it impossible to pull it out intact.

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