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When a Ceramics Expert…
By David L. Ahearn P.E.
and Fred Schmidt, PhD, P.E.
Engineering Systems Inc.
[email protected]
F
amiliarity with water closet devices implies we take them
for granted, but toilets can be the source of major property
losses. The possibility for user error, chemical attack
(household cleaners), installation error, and manufacturing related
problems must be investigated for the source to be known. ESI
has investigated toilets that seemingly exploded due to failed
plastic pressure vessels, and others that have leaked due to poorly
tightened fittings. This article discusses a toilet that cracked
while no one was home, such that the homeowner came home
to water running down their stairs to greet them back from their
vacation.
Upon first sight the toilet does not seem highly damaged, just a
small crack down the side of the tank allowing a steady stream
of water to fall to the floor, rendering the float switch pointless
to shutoff the water (Left Photograph).
By breaking the fracture apart, we were able to look at the fracture
surface (Center Photograph). This revealed a line of material
Crack in the side of the tank
inconsistent with the vitrified china of a water closet tank.
This material was porous and not well bonded (Top Right).
The rest of the cross-section was of more normal appearance to
vitrified china, where the glassy phase of the porcelain has melted
and bonded the other particles together (Bottom Right).
The summary is that this toilet began to fracture the day it was
manufactured. Just because ceramics are brittle does not mean
that they always fracture quickly and completely. Think of a
car windshield hit by a rock. It may take months for the crack
to grow across the width of the car. Similarly, a small crack
can be frozen into a ceramic taking years to grow into a visible
water