Have hairline crack approx 2 inches long running from bottom rear of tank to the water dismissal hole? Or whatever it is called. Sounds like any porcelain crack repair is iffy, the model is a 1953 briggs with a unique matching color to the 1953 bathroom floor and wall tiles. I probably won't try to repair after reading below. However that was 6 years ago has any repair product been developed since?

Hi Grs60 and Welcome to The Plumbing Page. At AskMeHelpDesk.com. Does this crack run from the tank bolts? Back to you, Tom

Tom, no it starts at the main drain hole in the tank, and extends approx 2 inches to back of tank and starts curving upwards the back of tank. Nowhere near bolts.

Is it leaking? If not about all you can do is leave it alone. If you remove the tank,let it dry for a couple of days you may be able to epoxy the crack from inside.

Ma0641 took the words right out of my mouth. Shut the water off and sponge out the tank. Let it dry, you might use a hair dryer to hasten things along. Now caulk the crack with epoxy and let it cure before using. Good luck, Tom

Thx for answers. I have decided to replace so as to have "peace of mind" and no further thoughts of what may occur.

Here's a tip. DO NOT crank down tight on the tank bolts. Your tabnk will crack the first time someone leans back. Make sure the tank has about 1/4" of "give" when you install it. Good luck, Tom