Step 5 · Dry Fit and Install PVC Flange Assembly
First, slide the flexible transition coupling (e.g., a Fernco coupling) over the cleaned cast iron pipe. Next, prepare the PVC components. Cut a short piece of 4" PVC pipe that will connect the flange to the coupling. Apply PVC primer to the inside of the flange hub and the outside of the PVC pipe end, then apply PVC cement to the same surfaces and push them together with a quarter turn. Hold for 30 seconds. Now, insert the PVC pipe into the flexible coupling. Position the flange so it sits flat on the floor, with the closet bolt slots oriented parallel to the back wall. Use a nut driver or socket wrench to tighten the stainless steel bands on the flexible coupling, securing it to both the cast iron and PVC pipes. Do not overtighten, but ensure it is snug. Finally, secure the flange to the subfloor using appropriate screws (e.g., stainless steel or corrosion-resistant screws).