4" x 4" ProFlex Coupling (Cast Iron to PVC, Steel or Extra-Heavy Cast Iron)

These are a must have when transitioning in close quarters, and for any clean and correct transition from cast iron dwv pipe to schedule 40 dwv piping.

I used this to mate a 4" PVC pipe to a 4" cast iron pipe below it. Both are nominal 4" but the actual outer diameters are different with the CI being smaller. The rubber sleeve on this coupler has one side that is larger than the other to accommodate the difference, and I was careful to put the correct side each way, but the pipe still leaked. The cast side was not tight enough. I tried to tighten the sleeve over the cast iron even more by turning the torque clamp but it kept snapping above a certain pressure and it didn't matter anyways because it would just kink the metal and leave a gap that couldn't be sealed. I had to cut the cast iron pipe again which was not fun to get the coupler off and add an extra segment of PVC with an extra coupler. I bought a second one of these because the clamp on the first one was useless, but this time I caulked a ton of silicone both inside the rubber sleeve and along the edge of the outside bottom (three applications just to be sure). So far it's not leaking

We use the ProFlex Coupling to repair sewer stacks. They make a very sound connection between the cast iron and schedule 40.