You may want to look into one of the marine sealants, 3M and others manufacture them. You can probably find some equivelants (polysulfide, or polyurethane) in the paint departments at HD or Lowes. Just make sure they are listed for bath and kitchen.

: I have a acrylic tub having no overflow lip in back that leaks during a shower back behind the tile, and I have had to put silicone caulk bead between tub and ceramic tile to cure the problem. That works, but not for more than a few years. Problem seems to be silicone eventually separates from acrylic, leaving a water channel, no matter how well acrylic surface is prepared.

: I don't want to do this again. Home depot guy says phenoseal vinyl caulk is better than GE silicone.

: 1) Any opinions about durability of caulks or adhesion to acrylic?
: 2) Would putting a small "underbead"(perhaps unsightly) of a highly adhesive compound to "back up" the other caulk be a good idea? Any candidates that are waterproof?