Bathtub caulk is more than just a place to grow mildew. A well-placed bead of caulk keeps water from seeping behind the tub and ruining the floor and walls. If the caulk around a tub is peeling, cracked, or just plain icky, a quick trip to the hardware store and an afternoon without a shower could prevent a much more costly home repair.

Step 1: Remove the old caulk completely. This is the most difficult part of the job. There are several tools designed to help. A combination of a few different ones usually works best. Choose a plastic caulk removal tool, a flat-head screwdriver, a putty knife, a razor blade or a triangle head grout removal tool. Scrape away every last bit of caulk. Be careful to avoid scratching the tub or wall surfaces during the process.

Step 2: Once the old caulk is removed, clean the area thoroughly with bleach and water to remove any traces of mildew. After the area has dried, use a cloth soaked with denatured alcohol to clean and prepare the surface for caulk.

Step 3: Apply two strips of blue painter’s tape horizontally along the shower wall and tub, leaving a quarter-inch gap for the caulk to fill.

Step 4: Choose a latex-base mildew resistant tub and tile caulk with a two hour or less dry time. Cut the tip of the tube off at a 45-degree angle; the smaller the opening, the better. Use a long nail or wire to puncture the seal inside the caulk tube before inserting the tube into the caulk gun.

Step 5: Start at a corner where two walls meet and quickly apply a smooth, steady bead of caulk into the crack. Work fast, doing one wall at a time. Speed is more important than neatness at this point.

Step 6: Dip a finger into a cup of warm water mixed with a few drops of dish soap. Smooth the bead of caulk around the tub with the finger, wiping excess caulk onto a paper towel or disposable rag.

Step 7: Remove the painter’s tape while the caulk is still wet. Pull the tape straight out — not up — from the tub to assure a clean, tight seal.

Step 8: Wait at least four hours or so before showering to assure the caulk is well cured and the tub is well sealed.