Frankenplumbing

Do you need an adjustable plug for a slightly less than 3.5" diameter pipe end? We had that situation for our main drain cleanout in our basement, and nothing fit. The old metal cap had been broken getting it open, which seems to be a common side-effect of lazy plumbers around here who don’t want to work at getting a cap off without damaging it. The 3" adjustable plugs fell down the pipe. The 3.5" plug was too large, and the 4" plug was far too large.

Home Depot around here carries the Sioux Chief Test Titan mechanical test plugs:  http://www.siouxchief.com/Testing/Plugs-And-Caps/Test-Titan.698E7. Similar styles are made by Oatey, Cherne, and more. They have a plastic or metal bottom plate with a spoke sticking up, a rubber gasket, a plastic or metal top plate, and then a plastic or metal thumb screw or wing nut. The bottom plate and rubber gasket are supposed to fit in the pipe, the top plate is not supposed to fit in the pipe, and then you use the thumb screw to force the plates together, squeezing the rubber gasket outwards to create a tight seal.

The solution we found was to use parts from the 3" Sioux Chief mechanical test plug 882-3 (from Home Depot) and parts from the 3.5" Sioux Chief cleanout test plug 882-35 (from True Value). The rubber gasket from the 3.5" plug fit into the pipe with a little encouragement, but the bottom plate from the 3.5" plug was too wide. The bottom plate of the 3" plug fit into the pipe, but was too small to actually compress the 3.5" rubber gasket. So we took the top plate from the 3" plug, turned it over, and put it below the gasket. The 3" bottom plate presses against the inverted 3" top plate, which presses against the bottom of the 3.5" rubber gasket. Then we added the top plate from the 3.5" plug, and one of the thumb screws (they were interchangeable). A little mix and match, and we have a working plug for a 3.4" pipe end.

Another possible solution would have involved grinding down the outer edges of the bottom plate from the 3.5" plug to fit into the pipe. The bottom plate doesn’t need to be a tight fit against the interior of the pipe. It just needs to be large enough to press against the rubber gasket from below.