Q: I have resealed around my bath 3 times in the past year but it still splits open. I clean out the existing sealant, dry it all down, fill the bath with water and then reseal it. I leave it for a day to harden and keep it dry. But after about 2 months small cracks appear and they just get bigger.
A: The key to success is surface preparation. If you don't get the tub and wall surface perfectly clean, it doesn't matter what sealant you use--it will eventually fail. FYI filling the tub with water before caulking is meant to weight the tub, so that when the water is drained the tub will rise slightly to compress the sealant. It won't hurt but it won't always help because tubs are often installed in a way that prevents weight from moving them up or down. Anyway, if you want to see how a pro does this work, check out This Old House general contractor Tom Silva in the following link. He'll also give you some advice on sealants: http://www.thisoldhouse.com/toh/how-to/intro/0,,20050103,00.html?xid=yahoo-answers&partner=yes