The short answer: clean grout with a pH-neutral cleaner, warm water, and a stiff nylon brush — never vinegar, harsh acids, or wire brushes. If grout stays dark after cleaning, crumbles, or shows spreading stains near the shower, water is getting behind it, and it is time to reseal or regrout.
Grout complaints are the most common maintenance question JM Custom Tile and Stone hears from homeowners around Riverside, Corona, and Moreno Valley — usually some version of "the tile still looks new, but the grout looks awful." The good news: most dingy grout cleans up with the right (cheap) supplies. The important news: some grout problems are not dirt at all, and scrubbing harder makes them worse. After 40 years in the trade, here is how we separate the two.
Why Does Grout Get Dirty Faster Than Tile?
Glazed tile is essentially glass — nothing soaks in, so a mop handles it. Cement grout is the opposite: it is porous, sits slightly below the tile surface, and catches everything the mop pushes across the floor. Dirty mop water is the quiet culprit on most floors; the tile comes clean while the grout lines drink the gray water and slowly darken. In showers, add soap scum, body oils, and constant moisture, and grout becomes the hardest-working surface in the room. A penetrating sealer slows all of this down, which is why sealing is part of every install we finish — but sealer wears, and that is where maintenance begins.
What Is the Right Way to Clean Grout?
The routine we recommend to every client at handoff:
- Vacuum or dry-sweep first. Grit ground into wet grout lines is what turns them gray.
- Apply a pH-neutral tile cleaner diluted per the label, and let it dwell for a few minutes. Neutral means it dissolves grime without attacking the cement or the sealer.
- Scrub the lines with a stiff nylon brush — an old toothbrush works for small areas, a grout brush on a handle saves your knees on floors.
- Rinse with clean water and towel off. Leaving dirty rinse water to dry in the lines undoes the work.
- For deeper stains, step up to an alkaline cleaner or an oxygen-bleach powder made for grout — one product at a time, rinsed fully between attempts.
What Should You Never Use on Grout?
Half the grout damage we are called to repair was done by cleaning products, not by wear. Keep this list by the supply cabinet:
| Do | Don't |
|---|---|
| Use a pH-neutral cleaner for routine care | Use vinegar, lemon, or acidic cleaners — acid eats cement grout and etches natural stone |
| Scrub with a stiff nylon brush | Scrub with wire brushes or abrasive pads that gouge the lines |
| Use one product at a time, rinsing between | Mix chemicals — bleach plus ammonia releases toxic gas |
| Rinse and dry the lines after cleaning | Let dirty mop water dry into the grout |
| Reseal cement grout when water stops beading | Seal epoxy grout — it is non-porous and does not need it |
One more caution for natural stone: marble, travertine, and other stone surrounds are even less forgiving of acids and harsh cleaners than grout is. If your grout borders stone from one of our natural stone installations, pH-neutral is not a suggestion — it is the rule for the whole surface.
When Is It a Water Problem, Not a Dirt Problem?
This is the distinction that saves showers. Dirt sits on top of grout and responds to cleaning. Water problems live underneath and do not. The tells:
- Grout that darkens again within days of a thorough cleaning, especially low on shower walls or along the pan.
- Dark spots that spread along a grout line instead of fading with a scrub.
- Cracking, powdering, or missing chunks — paths for water to reach the wall behind the tile.
- A mildew smell that returns fast no matter how well the room is ventilated.
If any of those signs sound familiar, stop scrubbing and have it looked at. What separates a simple regrout from a torn-out shower is time — our post on how long a shower remodel takes shows what the full rebuild involves when water has gotten too far.
When Should Grout Be Resealed?
Use the bead test, not the calendar. Drip water on a clean, dry grout line: beading water means the sealer is still doing its job; water that soaks in and darkens the line means the grout is drinking again, and it is time to reseal. Cleaning frequency, hot showers, and scrubbing all wear sealer down, so a busy family shower fails the bead test long before a guest bath floor does.
Resealing itself is honest DIY territory: clean the grout thoroughly, let it dry completely — cement grout holds moisture longer than it looks like it does — then apply a penetrating sealer per the label and wipe the excess off the tile faces before it hazes. For where the DIY line sits on bigger jobs, our guide to tile work you can DIY is the honest map.
When Is Regrouting the Better Answer?
Sealer protects sound grout; it cannot rebuild failed grout. Once lines are cracked, crumbling, or stained through their full depth, the fix is mechanical: rake out the old grout, clean the joints, and pack in fresh — often an epoxy or high-performance grout that resists stains and never needs sealing. Done well, a regrout makes a tired shower look newly built for a fraction of a remodel.
The honest caveat: regrouting only helps if the waterproofing behind the tile is still sound. Regrouting a shower whose membrane has failed just puts a fresh face on a wet wall. That judgment call — regrout versus rebuild — is exactly what we assess on shower tile and bathroom tile visits across the area. Every JM Custom Tile and Stone crew member is a tile specialist, the work is guaranteed, and we leave the house cleaner than we found it.
Grout Care: Common Questions
How often should grout be resealed?
Test it instead of following a calendar: drip a little water on a clean, dry grout line. If it beads on the surface, the sealer is still working. If it soaks in and darkens the grout, it is time to reseal. Shower grout usually needs attention more often than floor grout because it gets soaked and scrubbed far more.
Can I use bleach on grout?
Diluted chlorine bleach can lighten stains on plain white cement grout, but it will strip color from pigmented grout, damage sealer, and etch nearby natural stone. Never combine it with ammonia or any other cleaner — the mix releases toxic gas. An oxygen-bleach powder is a gentler choice, and pH-neutral cleaner should still be your everyday default.
Do steam cleaners damage grout?
Occasional steam cleaning is fine on sound, sealed cement grout, but frequent high-pressure steam can degrade sealer and wick moisture into hairline cracks. If you steam clean, do it sparingly, keep the nozzle moving, and check afterward whether water still beads on the grout lines.
What is the difference between resealing and regrouting?
Resealing is maintenance — a penetrating sealer soaks into sound grout and slows down stains and water absorption. Regrouting is repair: raking out grout that is cracked, crumbling, or permanently stained and packing fresh grout in its place. Sealer cannot fix failed grout, so if lines are breaking up or a shower shows spreading dark patches, resealing over the problem only hides it briefly.
