OATEY 271713 Cherne® 3 in. Clean-Seal® Plug

Both. The Clean-Seal plug is built to seal plastic cleanouts and the hard-to-seal cast iron threaded ones, where the threads are often corroded or out of round. The natural rubber body inflates to conform to the bore instead of relying on clean threads for a seal.

Up to 13 psi, which works out to about 30 feet of water column. That covers a typical two to three story stack test. If you are testing a taller column than 30 feet, this plug is not the right tool for the bottom of that stack.

Inflate to 35 psi (2.4 bar). The inflation valve fitting takes a 1/4 in. thread, so a standard 1/4 in. air chuck or hand pump connection mates up. Do not confuse the 35 psi inflation figure with the 13 psi the plug will hold back once set.

A standard test ball is a plain bladder that plugs the line and backs water up behind it, so when you deflate it the head dumps out at you. The Clean-Seal design keeps the work area and the plumber dry, with no backsplash when it is released. It also uses high-impact ABS threads rather than an all-rubber body, which is what lets it grab threaded cast iron cleanouts.

No. The inflation valve fitting on the Clean-Seal plug is removable and field repairable, so a leaking or damaged valve can be swapped out on the job instead of scrapping the plug.

Yes, within its limit. Set at 35 psi inflation, it will hold a static column up to 13 psi or 30 feet. For a plumbing rough-in test on a stack of two or three floors that is enough; above 30 feet of head you need a plug rated for higher back pressure. The rubber body gives the leak-free seal that holds the column.

Order it as Oatey 271713. It weighs 0.85 lb and the rubber body is black, so it is light enough to carry a couple of sizes in the truck without thinking about it.