Clean Grout Lines in Shower Tile

Grout darkens. That's what grout does when water runs over it every day for months or years. The cement-based material between your tiles absorbs soap residue, body oils, hard water minerals, and mildew spores until what was once crisp white or bone becomes a dingy grey-brown shadow of itself. The good news: grout cleans up remarkably well with the right approach and a bit of elbow grease. The secret to truly clean grout isn't a miracle product—it's methodology. You need an alkaline cleaner to cut through soap scum and oils, mechanical agitation to pull grime from the porous surface, and enough dwell time for chemistry to do its work before you start scrubbing. Most people scrub too soon and rinse too fast. Do this right, and your grout will look newer than it has in years.

1. Start With a Bone-Dry Canvas. Remove all bottles, soap dishes, and bath accessories from the shower. Squeegee the walls to remove standing water, then run a fan or open a window to let surfaces dry for 30 minutes. Cleaning paste sticks better to dry grout and won't get diluted by residual moisture.
2. Make Your Own Cleaning Paste. Combine ½ cup baking soda with just enough water to form a thick paste—about 3-4 tablespoons. The consistency should be like peanut butter, thick enough to cling to vertical surfaces without running. For heavily stained grout, substitute hydrogen peroxide for water to boost cleaning power.
3. Pack Paste Deep Into Lines. Use a small putty knife or old toothbrush to apply paste directly onto grout lines, working in 3-4 square foot sections. Press the paste into the grout, covering the entire line thickness. Don't coat the tile faces—keep application targeted to grout only. Let the paste sit for 15 minutes.
4. Scrub Like You Mean It. Use a stiff nylon grout brush and scrub each grout line with firm, back-and-forth strokes. Apply real pressure—you're trying to dislodge material that's embedded in porous cement. You'll see the paste turn grey or brown as it pulls out grime. For corners and edges, switch to an old toothbrush.
5. Rinse Until the Water Runs Clear. Use a spray bottle filled with clean water to rinse each section, then wipe with a damp microfiber cloth. Make multiple passes—residual baking soda leaves a white haze if not fully removed. Check your work as you rinse; if grout still looks stained, repeat the paste application and scrubbing on those areas.
6. Bleach the Holdouts. For grout that's still discolored after the baking soda treatment, mix 1 part bleach to 10 parts water in a spray bottle. Spray directly on stained grout, let sit for 10 minutes, then scrub again with your grout brush. Ventilate well—run the bathroom fan and crack a window. Rinse completely with water.
7. Document Your Before-and-After. Wipe down all surfaces with a dry towel, then let the shower air-dry completely for several hours. Once dry, inspect your work under good light. Clean grout should be uniform in color and noticeably lighter than before. If you see remaining dark spots, they may be permanent stains or mildew that's penetrated too deeply.
8. Seal In Your Victory. Once grout is completely dry (wait 24 hours), apply a penetrating grout sealer with a small foam brush or roller. Work it into the grout lines, wipe off excess from tile faces immediately, and let cure per manufacturer directions. Sealer makes future cleaning easier and slows re-staining significantly.