In residential plumbing, brass, copper, and cast-iron closet
flanges have largely been replaced by ABS and PVC flanges.
Other than that, today's closet flanges look essentially the
same as those made 50 years ago.
They also suffer from many of the same problems. And when
closet flanges break or are improperly installed, toilet bowls
can rock and shift position, allowing water to leak out and
foul gases to escape. This can lead to structural damage and
unsafe and unsanitary conditions.
While plastic flanges perform just as well as their metal
counterparts when they're properly mounted and securely
anchored to the floor, they are somewhat less forgiving of
installation errors. Fortunately, repairing or replacing a
damaged plastic flange is often easier and safer than replacing
a damaged metal flange, which can involve soldering, pouring
lead, and working with a flame around dangerous gases.
Repairing a Broken Flange
Plastic closet flanges are especially susceptible to breakage
when the toilet is overtightened or when the flange isn't
attached evenly to the floor. The breaks generally occur at the
bolt slots, since the rim of the bolt slot is the weakest part
of the flange.
Because two bolts are required to properly hold a toilet bowl,
a break at either one of the two slots can make it impossible
to pull the toilet tightly against the flange and the
This problem can be fixed with an inexpensive, crescent-shaped
metal part called a spanner flange (see Figure 1). Slipped
underneath the edge of a broken plastic or metal flange, the
spanner flange bridges the broken area and provides a secure
mount for the closet bolt.
Figure 1. Spanner
flanges (A) make repairing broken bolt slots easy. First, the
author removes the screws holding the closet flange in place;
then he inserts the closet bolt (B). Next, he slides the
spanner under the broken portion of the flange (C). While
reattaching the closet flange to the floor, he threads some
screws through slots in the spanner flange to help hold it in
position and strengthen the assembly (D).
Some spanner flanges have predrilled holes that allow them to
be easily anchored or screwed in place, but in some instances
anchoring to the floor is not possible or even necessary.
When only a small section of the closet flange has broken away,
for example, a heavy spanner alone can provide sufficient
strength once it's slid securely under the remaining portion of
the damaged flange. With larger breaks, however, I try to
anchor the spanner with screws when working above wood
flooring, or with lead anchors when working over
Sometimes the top of the closet flange is set below or even
with the floor surface, which can make it difficult to slide
the spanner flange into position under the broken flange. In
such cases it's usually easier to simply anchor the spanner in
place on top of the flange instead of underneath it.
When both sides of the flange are broken, I use the Super Ring
closet ring replacement (Superior Tool Co., 800/533-3244,
www.superiortool.com; Figure 2), which is
rugged and stronger than many new flanges. The key to a
successful repair with the Super Ring is getting it to sit
tight against the existing flange.
Figure 2. When both bolt slots are broken,
the author installs a closet ring replacement over the existing
closet flange (A). After marking and drilling holes in the slab
for anchors, he applies a bead of silicone caulk (B), then
positions the ring on top of the existing flange and sets the
anchors (C). With the wax ring in place, the flange is ready
for toilet installation (D).
Because the Super Ring isn't very thick, it can be used with
both flush-mounted and surface-mounted flanges. But
occasionally I find that when the ring is installed on a raised
flange, one or more of the outer perimeter ears needs to be
trimmed with a hacksaw or grinder to prevent it from hitting
against the outside base of the bowl.
Removing a Plastic Flange
Unlike a lead joint that can be melted or picked apart, a
solvent-welded plastic joint can rarely be separated cleanly,
if at all. So if it's possible to get access below the flange
via a crawlspace or a basement, cutting the plumbing back and
installing a new section of pipe and flange is sometimes
However, when the toilet sits above a finished ceiling or is on
a concrete slab, I remove as much of the damaged flange as
possible from above and then use one of several specialty
flanges on the market to replace the damaged flange.
There are a couple of different tools that help me do this. One
is a miniature circular-saw blade (Atlanta Special Products,
800/327-3552, www.pace-asp.com) attached to a shaft
mounted on an electric drill (Figure 3). The saw cuts through
the walls of the flange hub and pipe from the inside. This
technique makes quick work of flange removal, though it does
require a strong, steady hand for clean cuts.
Figure 3. The author
uses a small shaft-mounted saw blade powered by an electric
drill (top) to separate a plastic closet flange from its drain
without disturbing the finish flooring (bottom).
Personally, I usually prefer to use a cable saw. Working with
this tool takes a little more time and effort, but it's less
likely to damage the floor covering around the flange.
A cable saw is basically a heavy steel leader wire that you
slip under the flange surface just above floor level and pull
back and forth in a sawing motion to cut through the PVC flange
(Figure 4). These saws are sold at plumbing and hardware
outlets, but you could also probably fashion one from items
found in your fishing tackle box.
Figure 4. In cases where
a closet flange is surface-mounted (rather than flush to the
floor), the author slips a simple cable saw (A) under the
flange and pulls it back and forth in a sawing motion to cut
through the plastic (B). He removes the damaged flange (C),
cleans up the cut with a utility knife (D), and then installs a
replacement flange that slips inside the existing
Replacing a Flange
Once I've removed a flange, I can replace it with any of
several different types of plastic flanges designed for
retrofitting into the remaining drainpipe.
For example, Oatey's cast-iron flange replacement
(888/466-2839, www.oatey.com) has an expandable gasket;
once the fitting has been inserted into the existing 4-inch
cast-iron or plastic drainpipe and secured to the floor, the
gasket seals the flange to the inside pipe wall. This fitting
comes in both PVC and ABS plastic (Figure 5). Plastic
replacement flanges are also available in sizes that fit
tightly inside 4-inch and 3-inch PVC and ABS plastic pipe. Once
the top or flat portion of the old flange is removed, these
fittings are solvent-welded inside the pipe.
Figure 5. This plastic
replacement flange has an expandable gasket, allowing it to be
used with both cast-iron and plastic pipe (A). Replacement
flanges also come in various diameters to fit 3- and 4-inch PVC
and ABS drainpipe (B). After priming and applying cement to the
fitting and the drain (C), the author inserts the new flange
Whenever I'm using a 3-inch replacement flange, I check the
outlet of the toilet bowl to be sure it will fit inside the
flange opening. If it won't, I lower the flange so that it sits
flush with — or slightly below — the finished level
of the floor; the flange and bowl outlet should not touch when
the bowl is set. No matter what fitting I use, I make sure it's
screwed or anchored firmly to the floor. Otherwise, the flange
could be pulled loose as the toilet is tightened above
I've seen flanges fastened with drywall screws and even
16-penny nails, but I always opt for tapered brass or stainless
steel wood screws; they should have wide heads that won't pull
through the flange and be long enough to fully penetrate the
subfloor (11/4 inches is usually fine).
Reinforcing Damaged Flooring Around the
It's not uncommon to pull a toilet from the floor and find
serious damage to the wood immediately around the flange. While
rot is usually the culprit, sometimes the damage is as much
from the original installer's overcuts as it is from a leaking
If there isn't a solid surface for screws to grab hold of, the
plumbing alone will end up having to support the flange. With
some cast-iron plumbing you might get away with this, but not
with plastic plumbing.
Of course, the best way to take care of this problem is by
repairing or replacing any damaged framing, flooring, and
subflooring so that the flange can be securely fastened to
sound material. But when repair isn't an option or when damage
is limited, I use flange support plates to reinforce the floor
and provide a solid anchoring surface.
To Caulk or Not to
Some plumbers, contractors, and
home inspectors believe that the joint between the
base of the toilet and the floor should not be
caulked, reasoning that a caulked joint will
prevent a homeowner from detecting when the wax
seal has failed. But water that escapes from a tub
or a shower door — or that is splashed by
overzealous mopping — is far more likely to
be a problem when the bowl is not caulked than when
it is; many stained ceilings are caused by water
flowing under the bowl and through openings around
the flange. Caulk also helps hold the bowl to the
floor, preventing movement that can cause premature
failure of the wax ring. For these reasons and
others, both the International and the Uniform
Plumbing Code require fixtures that come in contact
with the wall and floor to be sealed.
These heavy-gauge galvanized steel plates — which come
in pairs shaped to fit under most bowls — slide under
both sides of the flange and extend to areas where there's
likely to be sound wood (Figure 6). The installer screws the
plates to the flooring, then drills holes in them and screws
the flange to the plates.
Figure 6. When there's
minor damage to the flooring around a closet flange, the author
reinforces the connection between the flooring and closet
flange with galvanized steel flange support plates (top). He
screws the plates to sound flooring either in front of or
behind the flange (bottom) and then fastens the flange to
Flange supports aren't usually visible beneath an installed
toilet, but when the fit isn't perfect, I cut and customize the
plates for a clean fit, using a hacksaw or grinder.
Extending a Flange
Ideally, closet flanges should be set so that they rest on the
finished floor, but during the rough-in process, they are often
installed too low.
On a slab floor, for instance, the flanges might get
mistakenly glued in place below the finished level when the
plumber sets them before the concrete pour.
Sometimes flanges are set too low because of changes in floor
coverings: Perhaps the homeowners belatedly decided they wanted
to switch from the original plan's vinyl to a thicker tile
When flanges are only slightly low — 3/4 inch below a
slab floor or 3/8 inch below a wood floor — I compensate
with 3-inch closet bolts (standard bolts measure 21/4 inches
long) and double the wax rings.
But with truly low flanges, I install a flange spacer, which
is essentially the top portion of a flange sealed to the
original flange surface (Figure 7).
Figure 7. Flange
spacers (top) can be used to raise a closet flange installed
below the level of the finished floor (bottom). Multiple
spacers are fine, but each must be sealed to the surface below
with silicone caulk and securely fastened to the
Since flange spacers are easy to install and inexpensive, I
use them whenever I'm in doubt and don't want to risk a leak;
multiple spacers are acceptable as long as they are sealed
between each layer. (Keep in mind, though, that some
manufacturers recommend no more than three.)
After I stack and seal the spacers — some manufacturers
specify RTV (room temperature vulcanizing) silicone caulk, but
some designs can be solvent-welded together — I drive
long screws or anchors through the layers until either the
screw threads into the subfloor or the anchor penetrates any
concrete around the drainpipe.
Then I set the toilet in the normal fashion with a wax ring
and closet bolts.
Even with a good solid flange, toilets installed on uneven
floors can rock. This motion can work the wax ring loose or
cause it to be pressed from under the bowl or into the
To steady the bowl, I use lead or plastic wedge-shaped shims
(Figure 8); I keep them in place and out of view by pressing
them just under the edge of the bowl and sealing the bowl to
the floor with caulk.
Figure 8. Plastic shims
help prevent a toilet from rocking on uneven
Another option is to apply tile grout — rather than
caulk — around the base of the bowl to hold the shims in
place. Once the grout sets up, it fills in the uneven gaps
around the bowl and provides some additional support.Kenny Hartoperates Hart's Plumbing and
Heating in Virginia Beach, Va., with his father, Ken Hart