When my husband and I moved into our house, there was always the faint smell of urine in the downstairs bathroom, which I couldn't explain. We have no children of our own at this point, but the previous owners had three little boys. Sure enough, my husband pulled up the toilet to look underneath. It was NOT pretty. There was TONS of old urine underneath... I won't go into detail. Once cleaned, the bathroom did not smell of urine anymore and hasn't since. We haven't used any caulking, since we don't have kids and have heard you shouldn't do that. But if I have a little boy, you had better bet that I will be getting that caulking gun out!