In this video, This Old House plumbing and heating expert Richard Trethewey shows how to fix that wobbly toilet by replacing the toilet flange
1. Use a small sledgehammer and cold chisel to separate the old cast-iron closet flange from the toilet's drainpipe, known as the closet bend.
2. Pry free the loosened closet flange with a flat bar.
3. Set the new compression flange over toilet's drainpipe, and then trace around it with a marker.
4. Use a hammer and cold chisel to chop out any tile that's preventing the flange from sitting flat without wobbling.
5. Press the rubber gasket onto the new closet flange; be sure the gasket's tapered edge faces down.
6. Set the brass ring on top of the rubber gasket, and tap it down with the hammer.
7. Use a ratchet wrench to tighten the four stainless-steel screws that secure the flange to the floor.
8. Insert two new closet bolts into the slots in the closet flange.
9. Press a new wax ring tight to the flange.
10. Set the toilet on top of the flange, making sure the two closet bolts pass through the holes in the toilet's base.
11. Onto each closet bolt insert a white plastic base, brass washer and hex nut.
12. Alternately tighten each nut with a ratchet wrench, being very careful not to over-tighten them.
13. Trim the closet screws down to size with a close-quarter hacksaw, then snap on the plastic covers.
14. Reconnect the water-supply line to the toilet.
15. Turn on the water by opening the toilet's shut-off valve.
16. Allow the toilet to fill, then flush the toilet and check for leaks.
17. Grab each side of the toilet and try wiggling it. If necessary, very carefully tighten each closet bolt a little more.