How to Replace Bathtub Caulk

Caulking tools on a bathtub.
What You'll Need
razor blade or utility knife
rubbing alcohol
Kilz spray (optional)
White or clear caulk (must be for bathrooms)
Caulking gun (optional)

You will be able to tell when it comes time to replace your bathtub caulk. It will simply start to come apart or turn dark in color. Sometimes this is because it wasn't installed properly; sometimes it's just worn out. Another thing to consider is that if your bathroom experiences a high level of humidity and not enough air flow, the continual dampness can contribute to the weakening, peeling, or darkening of your bathtub caulk. Regardless of the cause, you can easily replace bathtub caulking in four steps, as detailed below. Keep in mind that before beginning the process, you should gather the appropriate materials to have at your disposal. Once you start applying new bathtub caulk, you won’t be able to leave the job until it’s complete.

Note: Be sure to use caulking that's made specifically for bathroom or kitchen use, which usually have anti-mold and mildew additives in it. Once the additives wear out over time, however, you may start to notice an accumlation of mold or mildew.

Step 1 – Remove the Old Caulking

Remove the old caulking with a razor blade or utility knife. You can also use an oscillating tool with a flexible blade, which may reduce the time necessary on this step. This can be a tedious task, depending on how much is left and what type of caulking it actually is. Silicone caulk is usually harder to remove than latex caulk. (Keep this in mind when you buy the replacement caulking, if you plan on being in this house for a long time and may have to replace the caulk again down the road.) It's best to try using a new razor blade to scrape off the caulk as carefully as possibly. Using a dull blade may increase the chance of scratches to the surface of the tub. Removing all of the old bathtub caulk is vital to ensure the new caulking can adhere to the tub instead of being blocked by the debris.

Step 2 – Clean the Surface Area Thoroughly

After all the old bathtub caulk has been removed, sand down the area to remove any burrs so you have a smooth surface for the caulking. You will then need to clean the area thoroughly with rubbing alcohol. Rubbing down the area with rubbing alcohol will help ensure that all leftover residue is gone and that it dries out faster. Let the tub sit for one hour after cleaning.

Step 3 – Apply Mold Killer (Optional)

This step is optional but highly recommended, particularly if your bathroom is an area that's not well ventilated. Simply apply a product like Kilz mold-killing primer to all areas that the new bathtub caulk will go. Allow the area to dry completely for at least one hour.

Step 4 – Apply the New Bathtub Caulk

Someone applying caulk around a bathtub in a bathroom.

For this step, it's a matter of personal preference to use the caulking gun or to just apply the caulk directly from the tube. For beginners, it's sometimes easier to apply the bathtub caulk directly from the tube. This can be a messy step and it's hard to make it look professional if you have no experience, so plan on taking your time.

A caulking gun applying caulk to a bathtub.

Cut the caulking nozzle tip at a 45-degree angle. Apply the caulking in every crevice, being sure to leave no exposed areas. You will not be able to go back and redo this, so it’s important to get it all on the first time. Hold the caulking gun or tube at a 90-degree angle to the gap and either push or pull from one edge to another. After you've applied the bathtub caulk to a manageable area, go over it with your finger or a clean and dry cloth to smooth it out. Do this often so the caulking does not have a chance to dry before you can smooth it down.

This project is one that takes time and some effort to end up with a look that's clean, smooth, and protects your bathroom cracks and crevices from mold and mildew. Doing the job right will ensure the caulking stays put for some time.