My upstairs bathroom floor is leaking below to the kitchen. I am certain that the shower, commode or sink is not the problem as the plumber has been out. The grout against the tub has cracked and water seeps into quickly. I know I can help by having my teenagers be more careful, but I would like to fix the problem. I am guessing I need to remove the damaged grout and replace it. Do you have any helpful tidbits on doing this and is there a good way of getting a good seal against the tub? Thank you