Hot Topics: Unstick This Broken Nut

A slip-nut frozen onto a broken pipe.

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You never know what you’ll find when you start digging into old plumbing. Decisions made years ago by people you’ll never meet can put you in positions impossible to rectify with typical tools. When an old nut sits flush with a wall, frozen in place and impervious to your limited leverage, the Forum steps in to twist it free.

Original Post: Corroded slip nut in wall

smgdiy Member

I have a vintage 1954 bathroom. I am replacing the pop-up drain assembly in the sink and the trap arm broke when I was removing the P-trap. The slip-nut that connected the trap arm to the cast iron drain pipe fitting in the wall is corroded and just inside the plane of the wall. I can't afford to break any tiles, as they cannot be found today. I have applied WD40 a few times over the course of a couple hours, included using a small piece of wood to try to divert the WD40 onto the threads behind the slip nut, but I can't get a grip on the slip nut. I am letting it sit overnight to try again tomorrow, but would welcome any advice.

Highlights from the Thread

lawrosa Super Moderator

You could try cutting the slip nut in two places with a small hack saw blade. Don’t cut into the threads or you could have a leak down the road. Last resort is cut tile.

Is this under a vanity or a pedestal sink? You could always go from behind if there is a wall. You can cut that whole sanitary tee out and replace with PVC.

That’s all I got for ya!!!!!

Gunguy45 Super Moderator

WD40 is a poor product for breaking loose corroded fasteners. Liquid Wrench or PB Blaster would be better. Pro's may have other suggestions, but I'd probably use a one hand hacksaw and partially cut the nut then split it.

ray2047 Group Moderator

I'd use a Dremel and a carbide disk. Probably take more than one of the cheap discs.

toolmon Member

First thing I would do is collapse the brass tube inside and pull it out with pliers. Then you can get a puddle of PB Blaster right inside the nut. To unscrew it, or try to anyway, tap a sharp chisel to bite into the nut and keep tapping in a counter clockwise direction. If the pipe in the wall is solid in place, you may get lucky. This is the reason I always put teflon tape on plumbing threads that don't really need it.

PJmax Forum Topic Moderator

Maybe a tightspot wrench from Superior Tools and available thru Sears. Looks like it may work.

Superior Tool 1-1/2" Tightspot" Wrench - Tools - Plumbing Tools - Pipe Wrenches & Pliers

joecaption1 Member

Bet your going to end up opening up the wall. It was installed way to close to the wall.

smgdiy Member

And the winner is!


After I got the brass tube backed up like this, I used the Dremel wire wheel brush around the inside. When I put the pliers on the slip nut, it moved easily from all the WD40 I applied yesterday and the Liquid Wrench I have been using today. Now I have to finish prying out the rest of the old trap arm, which is totally corroded to the inside of the cast iron pipe.