Step 7 · Install the New PVC Flange
Remove the flange from the dry fit. Ensure the rubber gasket is properly seated on the flange. Insert the flange back into the cast iron pipe, pressing it down firmly until it rests on the floor. Use a wrench or socket set to begin tightening the compression bolts on top of the flange. Alternate between the bolts, tightening each one a little at a time, similar to tightening lug nuts on a wheel. This ensures the rubber gasket expands evenly against the inside of the cast iron pipe, creating a strong, watertight seal. Tighten until snug and the flange feels secure. Do not overtighten.