As a Plumber I say get a new one , weve tried to fix them but it doesnt allways work. As well once you get a crack in it you loose all its strength. The slightest tap and down she comes. : : I have a slightly cracked : : cracked toilet tank which has a : : slow drip leak. The crack is in : : the corner of the tank and does : : not extend to any of the : : openings in the bottom. Before : : going to the trouble of : : replacing the tank would it : : possible to apply something : : over the crack inside the tank : : to stop the leakage and prevent : : further cracking? If so, what : : would you suggest? Thanks: Drain the tank down. Put silicone in the crack. And let dry for an hour or two before filling back up.