New caulk around a bathtub lasts only when failed sealant is removed, the surface is clean and completely dry, and the product is compatible with wet areas. Caulk should not be used to hide a leak coming from behind the wall or from the drain.
Remove old caulk back to firm edges
Cut and peel the old bead without scratching the tub or wall. Remove residue with a tool or product compatible with the surface, and do not apply new caulk over loose or mold-contaminated material.
Clean and let the joint dry completely
Remove soap film, grease, and dust, rinse, and let trapped moisture leave the joint. Sealing a damp surface reduces adhesion and can trap water behind the new bead.
Apply a continuous bead of the right size
Cut the nozzle for a bead slightly wider than the gap, move at a steady pace, and tool it only enough to contact both sides. An oversized bead does not compensate for a poorly prepared joint.
Allow the full cure time before getting it wet
The required dry time depends on the product, temperature, humidity, and bead size; follow the label rather than a universal number. If water is emerging from behind the joint, stop using the tub and locate the leak before resealing.
Sources
- American Cleaning Institute — Cleaning Tips — General household-cleaning practices and responsible product use.