Use a Commercial Grout Cleaner

Apply a dedicated grout cleaner (spray or gel) to the grout lines, wait the time specified on the label, scrub with a stiff brush, and rinse thoroughly. Products like Zep Grout Cleaner or Black Diamond Ultimate Grout Cleaner are widely available and effective on moderate to heavy staining.

Why It Works

Commercial grout cleaners contain surfactants and mild acids (often citric or glycolic acid) formulated to dissolve soap scum, hard water deposits, and mildew that household cleaners leave behind. Gel formulas cling to vertical grout lines longer, increasing contact time and effectiveness.

Tips

• Always test in an inconspicuous spot first, especially on colored grout or natural stone tile
• Wear gloves and ensure good ventilation -- some products produce strong fumes
• Never mix commercial cleaners with bleach or ammonia
• Follow the manufacturer's dwell time exactly -- leaving acidic cleaners on too long can etch grout