The folks in this forum were kind enough to give me advice as to how
to do this so wanted to share my real life experience.
My friend was removing her toilet tank to replace the bolts and
washers (slight leak) and managed to break off a huge chunk from one
side of the tank -- about 8" long by 3" deep. Since it was a 3.5
gallon tank with no replacements available, choice was to glue it or
replace the toilet. The break was above the water line (OK, I did
lower the water in the tank a little to make that so) and on the side
of the tank facing the sliding glass doors on the tub.
Taking the advice here, I used a clear waterproof exoxy, $2.98 worth
of Devcon Two-Ton Epoxy. Mixed it in a plastic cup and applied it
with a plastic knife. Wiped off the excess with a little acetone and
I was done. We let the toilet sit overnight, did a final clean-up
with acetone and the toilet is back in service. The repair is as
strong as can be. I did increase the water-level in the toilet to
see if the repair was waterproof -- it seems to be but I didn't tempt
fate and lowered the level since the toilet flushed fine at the lower
So the cost of repair was $2.98 for the epoxy, a little Acetone (women
who wear nail polish most likely have this in their bathrooms) and a
plastic knife donated by Baja Fresh. As long as the break is fairly
clean, this is a repair anyone can make.
I did use regular expoxy rather than 5-minute epoxy. The regular
epoxy had a "work time" of 30-minutes so I didn't have to hurry in
making final adjustments to the "fit" and in cleaning up the excess.
DJ in VA