OATEY 271705 Cherne® 2 in. Clean-Seal® Plug

Both. The Clean-Seal plug seals plastic and hard-to-seal cast iron threaded cleanouts, which is the case the rubber body is there for, since threaded cast iron cleanout ports rarely give you a clean sealing surface. Nominal size is 2 in. (50 mm), and the natural rubber body goes in at a 2.38 in. (60 mm) deflated diameter, so it drops through a 2 inch port and expands to seal against the wall of the fitting rather than against the threads.

13 psi (0,9 bar), which works out to 30 ft. (9.1 M) of water column. That is the number that decides whether you can test a whole stack off one plug: 30 feet of head is roughly three stories of standing water above the plug. Taller than that and the plug is the wrong tool for the bottom of the stack. Inflate to 35 psi (2,4 bar), no more, and note that the inflation pressure and the back pressure rating are two different numbers, so do not read 35 psi as what it will hold.

The inflation valve is 1/8 in. thread, so a standard 1/8 in. inflation hose or gauge assembly threads straight on. The valve fitting itself is removable and field repairable, so if the valve gets damaged on a job you replace that fitting instead of scrapping the plug.

The Clean-Seal is the one to use when someone has to stand in front of the cleanout while it is under head. Its plug design keeps the work area and the plumber dry, no backsplash on release, which a plain test ball in an open cleanout will not do. It also has high-impact ABS threads, so it takes repeated in-and-out on threaded ports better than bare rubber. Where you are plugging mid-line or a bare pipe end rather than a threaded cleanout, a conventional test ball is the fit.

Volume is 0.017, and the plug weighs 0.3, so a hand pump handles it. There is no need for a compressor on a 2 inch plug, and a hand pump with a gauge makes it easier to stop at the 35 psi (2,4 bar) inflation figure instead of overshooting it.