My home is 21 years old and we have been fighting the caulking around our tub for the last 5! The bathroom is upstairs and has a window in it for ventilation. I recaulked it and the caulking almost melted within a couple of weeks. I thought perhaps I didn't let it dry enough before using the shower so pulled the remainder out and recaulked again. I waited a week before using the shower but the same thing happened. I then caulked and put "L" shaped plastic around the tub. It didn't stick either and again the caulking melted. I thought maybe there was water behind the tiles so pulled the caulking off and the plastic and didn't use the shower for two weeks and once again caulked. We are still fighting!! I thought maybe putting in a tub surround would get rid of the difficulty but then thought it might just be covering a "real" problem and could make it worse in a few years. We also have a problem with mold in that bathroom. I bleach the walls and ceilings but it continues to come back. I repainted in a special paint to deter mold but we still have the problem. We have other showers in the house and have never had such problems.However, this is the most used shower with my husband and 4 boys showering daily. PLEASE HELP!!! ps...I am using caulking specifically for tubs. Thanks.