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Remove the Broken Cast Iron Flange — Cut the Flange (Last Resort)

Beginner4 hours

Part of project

How to Remove a Stuck Bathtub Drain Flange · Step 4 of 5

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In this video

This is the most difficult step. Cast iron flanges are often sealed with lead. Use an angle grinder with a diamond wheel to make cuts into the flange itself, being careful not to cut the lead seal if possible. Then, use a heavy hammer and a chisel with a hand guard to break the flange apart. The key is to use the chisel to deform and break the lead seal between the flange and the pipe. Once the seal is broken, the flange can be pried out or knocked down into the drain pipe.

Goal: Plumbing Pipes Repair

  • This process creates a lot of dust and noise. Wear hearing protection, safety glasses, and a respirator/face mask.
  • Avoid grinding or excessively disturbing the lead seal to minimize toxic dust. Focus on breaking the cast iron first, then deforming the lead to break the seal.

Used in this video

  • Angle Grinder (Tool Type: Power Tools, Power Source: Corded Electric) — Cutting into the cast iron flange to weaken it for removal.
  • Diamond Wheel (Tool Type: Power Tools) — Attachment for the angle grinder, suitable for cutting metal and masonry.
  • Chisel (Tool Type: Hand Tools) — Breaking apart the cast iron flange and deforming the lead seal.
  • Hammer (Tool Type: Hand Tools) — Striking the chisel to break the flange and lead seal.
  • Pry Bar (Tool Type: Hand Tools) · optional — Prying up pieces of the broken flange.
  • Safety Glasses — Eye protection from flying debris.
  • Work Gloves — Hand protection from sharp metal edges.
  • Hearing Protection — Protecting hearing from the loud noise of the angle grinder.
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FAQs

What should I do if the drain key or wrench just slips, or the flange doesn't budge after applying penetrating oil?

If initial attempts fail, the flange is likely severely corroded or the putty is rock-hard. Apply more penetrating oil, like KROIL, and let it sit for several hours or even overnight to allow it to fully penetrate. If it still won't turn, your last resort is to carefully cut the flange using a rotary tool with a metal cutting wheel, making two opposing cuts without damaging the drain pipe threads.

Is it safe to cut the drain flange, and what precautions should I take?

Cutting the flange is a last resort and requires careful attention to safety. Always wear safety glasses and gloves to protect against metal fragments and sparks. Use a rotary tool with a metal cutting wheel, making two shallow, opposing cuts from the inside of the flange, being extremely careful not to cut into the drain shoe's threads below the flange.

How can I minimize the risk of damaging the bathtub or drain pipe during removal?

To prevent damage, protect the tub surface with a rag or towel if using a wrench or other tools that might slip. When cutting the flange, make shallow passes and continuously confirm you are only cutting the flange metal. Avoid excessive force, as that can warp the drain shoe or break connections further down the pipe.

Given this is a 'beginner' project, what are the most essential tools I absolutely need to have on hand?

Beyond basic safety gear, you'll definitely need a high-quality penetrating oil like KROIL, an adjustable wrench, and a specialized drain key or removal tool. For very stuck flanges, a rotary tool like the WEN 101-Piece Rotary Tool Kit with a metal cutting wheel (Stark 5 in. Metal Cut Saw Wheel) becomes essential. A putty knife and rags are also vital for preparation and cleanup.

Transcript
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And so now without any further ado, how to remove that damn cast iron flange. First you got to understand how it's mounted. And all probability yours is bonded to the cast iron pipe with lead. So what they used to do is they slipped on that cast iron flange. And then they stuffed oak them down there. And then they poured molten lead between the flange and the cast iron pipe. So you've got this monstrously strong bond there. And boy, I don't envy you if you have to remove it. So you're going to have to come out it with a chisel. Do make sure you use a chisel with a finger guard or else you're going to bang those fingers constantly. Use an angle grinder with a diamond wheel attachment. Do wear hearing protection because you're going to be using your grinder. Your angle grinder with a diamond wheel a lot. Hearing protection, wear face mask because it's going to it's going to get dirty. Like anything and everything you value in the bathroom just get it out because it's all going to be covered in cast iron filings. And more importantly, be careful not to hit that lead because you do not want to breathe lead dust. It is highly toxic. So avoid cutting into it. So yeah, I went at it with a chisel. I removed it piece by piece by piece. But even then it was, most of it was still in such good shape that no matter how much I banged on it, it just didn't shatter. So what finally did work for me is I took the chisel and I banged the lead. The lead's very soft, malleable, and eventually after banging it around that ring enough times, it actually broke the seal loose. And I was able to go down, to go down into the basement and knock it out from the bottom. So that's how I did. I mean, I tried everything. I tried to torch the grinding wheel. That's what wound up working is a chisel taken directly to the lead. Just bang on it until you basically have the lead ring slip off. And then you're able to remove the flange. Now in order to install the new OT PVC flange.

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