. Then I slid the flange into place and screwed in the Tapcons. Then proceeded with a normal toilet installation. Concrete Flanges If you run into a flange that is going into a concrete floor, make sure you screw the new flange in with Tapcons, not drywall-type blanks and screws. If your flange is loose or deteriorating, it can leak and erode the surrounding flooring, causing significant damage over time. :-( No matter. I have used that too and will agree that it works very well. Replace the toilet and tank and secure the flange … There are no anchors connecting the flange to the concrete slab.