Tub caulk turning pink or discolored (mildew)

Symptoms

• Pink or reddish film along the caulk lines
• Staining reappears within days or weeks of cleaning
• Slimy texture when touched
• Often appears near the drain or in constantly damp corners

Likely causes

• CommonSerratia marcescens bacteria (commonly called pink mold)This airborne bacteria thrives on soap film and moisture and is extremely common in bathrooms, not just poorly cleaned ones.
• CommonInfrequent cleaning allowing soap residue buildupSoap scum provides the food source this bacteria needs to establish and spread.
• PossiblePoor ventilation keeping the area constantly dampWithout good airflow, the moist environment this bacteria needs persists longer between cleanings.

What to do

1. Clean the pink staining with a bathroom cleaner containing bleach or hydrogen peroxide, following label safety instructions.
2. Scrub with a stiff brush, focusing on caulk lines and grout near the drain and corners.
3. Rinse thoroughly and dry the area with a towel.
4. If caulk is stained deeply and won't clean up fully, cut it out and replace it with fresh silicone caulk.
5. Wipe down the tub and caulk lines weekly with a bathroom cleaner to prevent soap film buildup going forward.
6. Run the bathroom fan during and after showers to reduce ambient humidity.
7. Consider a mold-resistant caulk for the replacement to slow future recurrence.

Tools and parts

• Stiff brush
• Bleach-based bathroom cleaner

When to call a pro

Not usually needed; a contractor is only useful if pink staining is part of a larger recurring mold problem throughout the bathroom.

Safety