How do you repair a toilet tank crack?

If water is leaking out of the tank you need to replace it. Any repairs done to it will be temporary and eventually it will leak again. Any glue or adhesive that works on ceramic will also work on the tank. Apply on both sides to seal the crack.

When you are ready to buy a new tank, find out what brand your toilet/tank is and buy a suitable replacement. Lowes, Home Depot and any other home improvement store will have them in stock or they can order it for you.

I dont think there is a way to safely fix a toilet tank crack. First off there is very cold water in it and it is made out of porcelin and that in itself is very hard to fix. a possible temporary fix would be to use a waterproof silicone. but like i said it would only be temporary. you would be better off to replace to insure it wont leak again.