Separating rusted Galvanized Steel Union?

Old 12-12-16, 09:19 AM
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Separating rusted Galvanized Steel Union?

I have a long length of 3/4" galvanized pipe which has been buried for a few decades. As you might expect, it has a light layer of rust on the outside.

I want to separate and remove a union WITHOUT messing up the pipe's threads, so I can thread either a new union or coupling on that pipe. My plan is to use a lot of PBlaster on the connection and let it soak for 24 hours, then repeat, then use two big assed pipe wrenches on it.

Anyone know of a better technique for removing the union while leaving the threads usable? I used conventional gray pipe joint compound on the fitting 30 years ago; no Teflon tape or modern white Rectoseal compound.
Old 12-12-16, 09:42 AM
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Heating the fitting (not the pipe) may help as well. But I would have a plan B in mind in case the pipe has rusted from the inside and just crumbles when you try to remove the union.
Old 12-13-16, 06:37 AM
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If it was mine I'd be spending my time digging it all up and replacing with some form of plastic pipe.
Steel pipe will rust out from the inside out 100% or the time even under the best of conditions like inside a home.
You'll have rusting issues on the inside and the outside.
First thing I do when buying a home that has steel plumbing is figure out what it's going to cost to replace it and take that amount off the asking price.
Old 12-13-16, 03:27 PM
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I agree with Joe, it would be better to tear out the galvanized and replace with PVC.

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