The toilet's closet flange serves a dual purpose, connecting your toilet to the waste line while holding the toilet to the floor. Like many plumbing fittings, it goes unnoticed until something goes wrong, and when something does, the results can be unpleasant. If the flange corrodes and breaks, water leaks out of the bottom of the toilet and sewer smells can escape into the bathroom. Replacing the flange isn't difficult if you understand its anatomy.
Understanding the Flange
A toilet flange has two parts, and each of them must be connected to something for the flange to fulfil its purpose. One part is a metal ring that screws to the floor directly under the toilet. The ring has two slots for the toilet bolts that extend upward through holes in the bottom of the toilet and hold it to the floor. Inside the ring is a short length of plastic waste pipe to glue to the waste line. You make this glue connection before bolting the flange to the floor, and you do it by working under the floor.
Removing the Old Flange
You have to remove the toilet to get to the flange. After unbolting and lifting the toilet out of the way, clean off the wax residue that remains around the flange opening with a putty knife, then unscrew the screws holding the flange to the floor with a screwdriver. Locate the coupling connecting the flange to the waste pipe. Cut through the pipe next to the coupling on the side farthest from the toilet with a hacksaw,.
Fitting a New Flange
Flanges come with different size waste pipes, so make sure your replacement matches the one you are taking out. Glue a coupling to the flange pipe with PVC cement, then drop the flange into place and glue the other end of the coupling to the waste pipe. If it doesn't reach, you may have to cut the waste pipe back a few inches and lengthen it by gluing on a second coupling with a short length of pipe. When the gluing is complete, the metal ring should be sitting on the floor. Screw it down with #10 galvanised screws or bolts.
The top of the metal ring on the toilet flange should come to the same level as the finished floor. If it is set too low, the wax ring doesn't seal and water leaks out, eventually corroding it and rotting the subfloor. You can increase the thickness of a conventional flange that is too thin by adding a flange extension, which is a metal ring that you place on top of the flange before you screw it down. If the floor is wet when you remove the old flange, give it plenty of time to dry and inspect it for rot before installing the replacement.