Mechanical connector Inexpensive but effective. Unlike some other mechanical plugs, this one has a large contact area with the pipe walls. In my situation, the three inch pipe was corroded and worn out. Those sold at local stores don't have enough rubber to fit the pipe snugly. This is a mechanical fork. In addition, the Jones Stephens Corporation T31003 Economy 3-inch Test Plug has a smaller base plate that easily fits into the tube. The only downside to this item is the wing nut. Replace the cheap wing nut with a higher quality wing nut. In addition, you should not buy other mechanical connectors sold in local stores. This is the one you want.