Step 3 · Apply Silicone Sealant

This is the step people usually slow down on. Go finger-tight first, then a quarter turn. No rush — replay the clip whenever it helps.

After confirming the fit, remove the extender ring. Using a caulking gun, apply a continuous, generous bead of 100% silicone caulk onto the top surface of the original flange. The bead should be about 1/4-inch to 3/8-inch thick. It is critical to apply the caulk on the flange surface, inside the ring of screw holes, to create a complete, uninterrupted seal that will prevent water and sewer gas from escaping between the old flange and the new extender.