How to Clean Grout That Won't Come Clean
Carpet Cleaning Apex • September 26, 2026 • 8 min read
You have tried the spray from under the sink, the old toothbrush and a Saturday afternoon on your knees, and the grout lines in the kitchen still look like pencil. Most advice on how to clean grout stops at “scrub harder,” which is exactly the step that did not work. Grout that won’t come clean usually needs a different chemistry, a better way to get the dirty water out, or an honest look at whether the problem is dirt at all.
This guide is a ladder. Start at the bottom rung, stop when the grout comes clean, and only climb when the rung before it has failed. It draws on the Tile Council of North America’s own guidance (TCNA, FAQ: Cleaning Grout), and it is written for the floors Apex homes actually have: builder-grade ceramic and porcelain in kitchens, laundry rooms and baths, with light grout that has turned gray.
Rung Zero: What Is Actually Wrong With the Grout?
Before cleaning anything, work out what you are looking at. Four very different problems all read as “dirty grout,” and only two of them respond to cleaning.
| What you see | Likely cause | Will cleaning fix it? |
|---|---|---|
| Even gray film, darkest in traffic paths and near the stove | Soil and grease in the pores | Usually, with the right cleaner and rinse |
| Black or pink spots in a shower or along a tub | Mildew or mold on the surface | Usually, with the right cleaner and drying |
| Grout lines low, sandy or scooped out below the tile edge | Worn or eroded grout | No; the grout needs repair or regrouting |
| Yellow, blotchy or peeling shine on the lines | A failed topical sealer or old floor finish | Not with a cleaner; the coating has to be stripped |
| One color on some lines, another on others | Old patch repairs or grout stained through | Cleaning shows it; color sealing or regrouting fixes it |
Run a fingernail along a few lines. Grout that is flush with the tile and hard is worth cleaning. Grout that is sandy, cracked or sitting well below the tile edge is worn out, and scrubbing it only speeds that up.
Pro tip: Clean one 2-foot test patch through each rung before you do the whole floor. It takes half an hour, tells you which rung works on your grout, and keeps you from spreading a product that does nothing, or worse, pulls color, across a whole kitchen.
Rung One: Alkaline Cleaner, Then Get the Dirty Water Out
The first rung is an alkaline cleaner and a wet vacuum, and it fixes more “hopeless” grout than anything else. TCNA says “it is better to clean grout with an alkaline cleaner (Spic and Span, Mr. Clean, etc.) than an acid based cleaner,” because grout is mostly cement, which is alkaline and is dissolved by acids.
The part most people miss is the rinse. TCNA calls the best method applying the cleaner “and then vacuum (‘shop vac’) up the dirty water,” then repeating with plain rinse water to remove the soap residue so it does not attract new dirt. Mopping leaves the loosened soil sitting in the lines; a wet vacuum removes it.
- Sweep and vacuum the dry floor so you are not making mud.
- Mix an alkaline floor cleaner at the label’s heavy-duty strength.
- Wet a section of about 3 by 3 feet and let it sit for the dwell time on the label. Do not let it dry.
- Scrub the lines with a stiff nylon grout brush (not wire).
- Pull the dirty solution up with a wet/dry shop vac.
- Rinse with clean water and vacuum again. Change the rinse water often.
If the test patch comes up several shades lighter, do the room this way and you are done. If it barely moves, climb.
Rung Two: Oxygen Cleaner for Organic Stains and Mildew
The second rung is an oxygen-based cleaner (products built on sodium percarbonate, sold as oxygen bleach). It is a common next step for organic stains: food, drink, mildew and the gray film on a shower floor. Follow the label for mixing and dwell time, test it on a hidden line first, and rinse and vacuum exactly as in rung one.
Showers and tub surrounds need one more step: drying. Mildew comes back on grout that stays damp, so run the bath fan during and after every shower and squeegee the walls. In humid Triangle summers, a bathroom without a working exhaust fan will re-grow what you just cleaned.
Rung Three: When Does Steam Help With Grout?
Steam helps when the soil is greasy and the cleaners above have loosened some of it but not all. TCNA says that if you are “unable to get your grout clean through conventional methods, you may also want to try steam.” Heat softens kitchen grease and body oils so they release from the pores.
A household steam cleaner with a small brush tip works on a patch at a time. Follow it with the same wet vacuum and rinse; steam moves soil, but something still has to remove it. On large floors, this is also where a professional tile and grout cleaning with hot-water extraction does the same thing faster, because it applies heat and pulls the water back out in one pass.
How to Clean Grout Without Damaging It: What Not to Use
Knowing how to clean grout is half knowing what to leave on the shelf. Several popular fixes damage grout or make it worse over time.
| Product or tool | Why to avoid it |
|---|---|
| Vinegar, lemon, or acid tile cleaners | TCNA: acids “attack the cement in the grout,” and strong acid “can strip some color out of grout” |
| Oil- or wax-based floor cleaners (Murphy’s Oil Soap, Pine-Sol) | TCNA advises against them for grout; they leave a film that holds soil |
| Chlorine bleach on colored grout | Can lighten or blotch the color; sealer makers also warn against it on sealed grout |
| Wire brushes and drill-mounted wire wheels | Scratch glaze and scoop out grout, leaving lines that hold more dirt |
| Mixing any two cleaners | Bleach mixed with ammonia or acids releases toxic gas. Use one product, rinse, then the next |
| A string mop and one bucket for the whole house | Spreads the dirty water from one room into the next room’s grout |
Natural stone (marble, travertine, limestone) is a separate case: it needs pH-neutral products, and the alkaline ladder above is for ceramic and porcelain. If you are not sure what your tile is, find out before you start.
When the Grout Still Won’t Come Clean
If the grout still looks dark after all three rungs on your test patch, it is probably not dirt. Go back to the table at the top. Grout that is stained through, patched in two colors or worn below the tile edge will not respond to more cleaning.
At that point the options are a professional deep clean to prove what cleaning can and cannot do, color sealing to even out grout that is sound but stained, or regrouting for grout that is cracked or eroded. The tile and grout cleaning cost guide covers what each option costs in the Triangle.
Once the grout is clean, keep it that way. Clean grout is open grout, and it will start soaking up soil and red clay again straight away. The next step is sealing, and how often you should seal grout depends on the product and the room.
Frequently Asked Questions
What is the best cleaner for grout?
An alkaline cleaner followed by a wet-vacuum rinse is the best starting point for ceramic and porcelain tile. TCNA recommends alkaline over acid cleaners because acid dissolves cement and can strip grout color. Save oxygen cleaners for mildew and organic stains.
Why does my grout get dark again right after I clean it?
Usually because the dirty water was never removed, or because the grout is unsealed. Mopping pushes loosened soil back into the lines, and open grout absorbs the next spill. In Apex, red clay tracked in from the garage entry is often the first thing to re-stain light grout.
Can I use vinegar to clean grout?
It is better not to. Vinegar is an acid, and TCNA notes that acids attack the cement in grout and grout makers do not recommend them. Repeated use slowly erodes the lines and can pull out color.
How do I clean black mold off shower grout?
Clean it with an oxygen-based cleaner, rinse, and then keep the shower dry. Surface mildew on grout usually lifts; if black spots come back within days, the grout or caulk behind it may be holding water. Growth that keeps returning in the same spot is worth a closer look at the shower’s waterproofing.
Is it worth hiring a professional to clean grout?
It is worth it when the ladder above has stalled or the floor is large. A professional tile and grout cleaning service uses heat and hot-water extraction to reach soil in the pores that hand scrubbing leaves behind. It also tells you honestly whether the grout is dirty or worn out.
Can you clean grout and carpet on the same visit?
Yes, and it is common in Holly Springs and Apex homes where the kitchen tile meets family-room carpet. The equipment overlaps with carpet cleaning, so ask for both when you request a free quote.
Grout That Won’t Come Clean in Apex or Holly Springs?
How to clean grout comes down to the right rung: alkaline cleaner and a wet-vacuum rinse first, an oxygen cleaner for mildew, steam for grease, and an honest check for worn or stained-through grout when none of them work.
If your floor has stalled on the ladder, tile and grout cleaning is available across Apex, Cary, Holly Springs, Fuquay-Varina and Morrisville. Request a free quote with a photo of the worst lines, and see the tile and grout cleaning cost guide for up-front pricing.
