OATEY 42744 3-1/2 in. Brass Cleanout Plug

The Oatey 42744 is the 3-1/2 inch plug in Oatey's countersunk and tapped brass cleanout plug line. It threads into a 3-1/2 inch tapped cleanout ferrule or fitting. If your ferrule is a different size, Oatey makes the same countersunk tapped plug in 1-1/2, 2, 2-1/2, 3 and 4 inch, so match the plug to the tapped opening rather than to the pipe label.

Yes, as long as the existing ferrule is tapped for 3-1/2 inch. The 42744 threads in the same way as the original brass plug, and brass on cast iron is the standard pairing precisely because it backs out again years later. Clean the ferrule threads and use pipe dope or sealant tape before setting the new plug.

Countersunk means the plug head sits flush or recessed in the ferrule rather than standing proud, which is what you want when the cleanout lands in a finished floor, under tile, or anywhere a raised square head would be a trip hazard or interfere with a cover plate. The 42744 is a countersunk and tapped plug, so the recess takes a wrench fitting rather than giving you an external boss to grab.

The 42744 ships as the plug only. You supply the thread sealant (pipe dope or PTFE tape) and the wrench. If the cleanout is in a finished floor you will also want a separate cleanout cover or access plate, since a countersunk plug does not include one.