Should I recaulk instead of scrubbing bathtub mildew?

If the bead is soft, black through the body, pulling away from the wall, or the stain returns in a few days after you dry the joint, cut the caulk out and replace it. Scrubbing only helps when the growth is on the surface.

Can I just bleach the mildew on an acrylic tub?

Regular bleach can yellow many acrylic and fiberglass shells and still leave growth in the caulk. Start with detergent and water. If you later use a bleach product, follow that label alone — never mix it with vinegar or ammonia.

Guide

How to Remove Mildew from a Bathtub

Ventilate, wet the stained caulk and corners so you are not brushing dry growth into the air, scrub with dish soap and a nylon brush, rinse, and dry the joint. Large, hidden, or returning growth needs a specialist. Never mix bleach with vinegar or ammonia.

Bathtub Mildew

Context

Conditions that change the method

Poor ventilation — Run the fan and open a window before you wet the tub. Dry brushing sends growth into the air.
Pet-safe — Keep pets and children out until the tub is rinsed and dry.
Delicate surface — On acrylic and fiberglass, use a nylon brush only — abrasive pads scratch the shell and give mildew more places to sit.

This is surface cleaning, not a mold-remediation or disinfection claim

If you have breathing, immune, or other health concerns, or the growth covers a large area or keeps coming back, stop and get help — including medical advice if you feel unwell. Do not dry-brush the caulk. Never mix bleach with vinegar or ammonia. If your eyes, skin, or breathing hurt, leave the room and get medical care. Rinse skin or eyes with water while you wait.

What you need

Dish soap and warm water
A nylon detail brush or old toothbrush
A microfiber cloth
A running fan or an open window

Ventilate. If anyone in the home is sensitive to mold, have them leave the room. Wet the caulk line, overflow plate, and corners with clean water before you touch them with a brush.
Work a few drops of dish soap along the stained joint and into the corners. Scrub in short, wet sections so you are not raising dry dust.
Rinse until the soap is gone. Leftover soap in the caulk is food for the next round of growth.
Dry the caulk, overflow, and basin. Keep the fan on after baths. A dry joint is the part of the method that lasts.

When to stop

If the same line darkens again within days, the caulk or wall behind it may be holding water. More cleaner will not fix a leak. Soft, black, or crumbling caulk should be cut out and replaced, not scrubbed forever. Growth that is widespread, hidden, or making people unwell is outside ordinary household cleaning.

What to avoid

Dry brushing or sanding the caulk line.
Mixing bleach with vinegar, ammonia, or an unknown bathroom cleaner.
Weekly bleach on acrylic or fiberglass — it yellows many plastic tubs and does not fix moisture.
Calling the tub disinfected because the stain looks lighter.

Products

What to use

Related guides

FAQ

Questions people ask

Should I recaulk instead of scrubbing bathtub mildew?: If the bead is soft, black through the body, pulling away from the wall, or the stain returns in a few days after you dry the joint, cut the caulk out and replace it. Scrubbing only helps when the growth is on the surface.
Can I just bleach the mildew on an acrylic tub?: Regular bleach can yellow many acrylic and fiberglass shells and still leave growth in the caulk. Start with detergent and water. If you later use a bleach product, follow that label alone — never mix it with vinegar or ammonia.

Sources

Mold Cleanup in Your Home — U.S. Environmental Protection Agency
Learn About the Safer Choice Label — U.S. Environmental Protection Agency