How to Loosen a Cast Iron Clean Out Plug

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Things You'll Need

  • Penetrating lubricant

  • Steel wire brush

  • Pipe wrench

  • Mallet

Many older homes still have old cast iron drain and sewer pipes rather than the PVC plastic pipes used in modern home construction. The end of the drain pipe has a removable cap plug. This plug allows access to the drain pipe for removing clogs and other obstructions. Cast iron has a tendency to rust, so drainpipe plugs that have not been removed in some time may seem molded to the pipe by rust. Loosening a cast iron clean-out plug from a drainpipe requires softening the rust enough to break it free.


Step 1

Spray the perimeter of the cast iron clean-out plug with penetrating lubricant. Spray the seam between the plug and the inside of the cast iron pipe. Allow the penetrating lubricant to work for 30 minutes.

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Step 2

Scrub the seam between the plug and the pipe with a steel wire brush. The lubricant softens and cuts through the rust and the wire brush helps to dislodge the rust further.


Step 3

Adjust the jaws of a pipe wrench around the protruding square peg on the end of the plug with the handle of the wrench pointing to the left.

Step 4

Tap the top pipe-wrench handle with a mallet while holding the wrench on the square peg to begin turning the drain plug counterclockwise. Once the cast iron clean-out plug begins to turn, continue turning it with the wrench until it is out of the drainpipe.


If the plug does not begin to move after tapping the wrench handle several times, spray more lubricant into the seam and wait another 30 minutes.



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