I recently replaced an older, water-guzzling toilet with a
low-flow model. The old toilet had been installed over a
ceramic tile floor on a concrete slab, so I anticipated an easy
swap. But one look at the rusted-out steel mounting rim on the
ABS-plastic closet flange told me I had a bigger fish to fry.
The old flange had to be cut off below slab level in order to
sleeve in a solid PVC flange. No way was I going to break up
the floor. Somehow, I had to cut the 3-inch drainpipe from the
inside. A picture of a 2-inch-diameter circular saw blade on a
long shaft formed in my head, but I didn't want to go chasing
all over town hunting for parts. After building a plywood sled
for my drill to control the cutting depth, I tightened a new
3-wing carbide-tipped slot-cutting router bit in my 1/2-inch
drill and stuck it down the pipe. But within a few rotations,
the bit rattled itself loose and went spinning down the drain.
I fished it out again with a long snake and a magnet and moved
on to Plan B.
After scouring three hardware stores without finding a
suitable metal blade, I spotted a 2-inch abrasive cutting disc
(The M.K. Morse Co., Canton, Ohio; 800/733-3377;
www.mkmorse.com; $2.50) with a 3/8-inch
arbor hole and recommended uses that included cutting plastic
pipe. The proprietary arbor was too short (and too expensive
for one-time use), so to make my own, I bought a 6-inch
carriage bolt, two nuts, several washers, and two fender
I added 2x4 legs to the sled, which set the disc at the right
depth to cut just below the flange collar. It took about five
minutes of clockwise rotation around the drain to chew through
the pipe wall, and a couple of vertical slashes with a recip
saw to remove the old flange in three chunks. I enlarged the
slab hole slightly with a cold chisel, then used a shop vacuum
and crevice nozzle to suck the sand away from around the stub
to accommodate the new flange. To reach the shortened drain
stub, I extended the flange collar with a cut-down straight
coupling and glued the sections together with solvent adhesive.
Four Tapcon screws anchored the flange, and the chipped slab
was repaired with topping cement.
1. Preserving the floor slab meant
cutting out the old flange from inside the pipe using a
homemade abrasive cutoff tool.
2. The author filed the
lugs round on a 3/8x6-inch carriage bolt to allow the head to
seat snugly against the washers that captured the abrasive
disk. The second nut locks the primary nut tight, while three
bench-ground flat spots at the other end of the bolt provide a
positive grip for the drill chuck.
3. The cut end of a
straight pipe connector was glued to the roughened end of the
common PVC closet flange to provide an extended collar to reach
the drain stub.4. In all the
excitement, the author forgot to remove the knockout in the
flange before installing the toilet and had to start over with
a new wax ring.