I am proud I managed to put a new flushing kit into older toilet tank, removed tank and hand hacksawed off a rusted bolt and put everything back together . . . Husband was a great assistant. NOW . . . I have a hairline crack in the tank, drips one drop every 5 minutes or so. Annoying to say the least.

Is there a epoxy, sealant spray to apply to the outside of the American Standard tank, as I really do not want to drain remove and take everything apart again.

I have heard of Flex Seal and the crack is barely visible and about 4 inches under waterlevel to?

I just drained the tank without removing it . . . so hopefully I can paint something on the inside?

Can I use this first on the inside of the tank when it dries? https://www.jbweld.com/product/waterweld-epoxy-putty

  • Please use the edit link underneath your post if you want to update it with new information. Thanks and welcome to the site.
    – Niall C.
    Aug 8, 2020 at 22:56
  • How did you get a crack? Did you over tighten a bolt? Forget Flex Seal...it doesn't last. It might be time to buy a new toilet. Otherwise use the epoxy described in the first answer. Sep 8, 2020 at 4:37

2 Answers 2


I personally would use pc-11 epoxy.

Drain and dry the tank, sand the area around the crack. Than mix up the epoxy using craft sticks and spread it over the sanded area. You can build up a few layers if necessary but pc-11 is pretty solid with just 1 relatively thin coat... Should be able to hold water in minutes but I would let it cure overnight for maximum adhesion

  • If you can spare it, let it cure for 24 hours.
    – Nelson
    Aug 10, 2020 at 5:58

Anyone looking at this question - the right answer is to get a new tank.

Yes you could "mend" it. But the problem is that to mend porcelain right you use basically a hard set epoxy. Should work great. Well now you are actually using the toilet when you sit you put slight pressure on the tank. This epoxy forms a crack over time or puts more pressure on porcelain. Then water does its thing, you go out of town for two days and your house is flooded because you didn't want to replace a $20-30 tank.

Mending it when the crack is below water line in tank makes no money/common sense at all.

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