: There is a crack in our toilet tank below the waterline. Previously it was patched with plumbers
: putty; this has lasted about 7 years. Will RTV do
: a better job, or is there something made for this
: repair?

Bob,
You must like living dangerously. Any tank with a crack should be replaced. I admit, seven years of good luck has been a good thing for you. How awful it would be if the tank split out the rest of the way, while you were away at work, and came home to a flooded home. It has happened. Good luck with your search for porcelain repair products.
Terry