Best Grout Whitener: Zep Cleaner Leads the Six

The best grout whitener for most bathrooms is Zep's Grout Cleaner and Brightener, a 32 fl oz acidic formula that lifts old stains from white and colored grout without heavy scrubbing. If your grout has moved past cleaning into permanent discolouration, switch to the Rainbow Chalk Markers Grout Pen 3-pack, a 7 mL white paint marker with a 5mm tip that recolours lines instead of cleaning them. The cost of getting this choice wrong is real. Reach for acid on marble or travertine and you will etch the stone.

Best grout whitener at a glance

How I narrowed six listings into a shortlist

I sorted the six picks by what they actually do to grout, because a whitener is not one product. It is three. Some strip stains chemically. Some cling to vertical lines. Some paint over the problem. Judging them against each other on a single scale is how buyers end up returning things.

The screening built up in three passes:

1. Buyer profile first. Renters and small-bathroom owners want a pen. Families with ceramic tile floors want a strong liquid. Anyone with natural stone needs an acid-free option, no matter what else they want.
2. Format second. Two liquids, one foaming spray, one gel, two paint pens. Each format got compared inside its own group before crossing over.
3. Published claims last. Dwell times, coverage figures, and surface compatibility as stated on the listing. Where a listing said nothing, I said nothing.

What got cut mattered as much as what stayed. Anything without a stated compatibility with common tile substrates was pushed down. Anything sold as a general bathroom cleaner without a specific grout claim did not make the shortlist. The APULITO gel kept its place because the listing states silicone sealant, tile and bathtub explicitly.

Chemical whitener or paint pen: which do you actually need?

This is the deciding question, and most guides skip it. A best grout whitener liquid, like Zep's Cleaner and Brightener, lifts dirt out of porous grout. A grout pen paints white pigment over the top. They solve different problems, and using the wrong one wastes an afternoon.

Use a chemical whitener when the grout was white originally and has darkened from soap scum, body oils, food splashes and mildew. The colour is under the dirt. Bring the dirt out and the grout looks new. This is most bathrooms younger than five years.

Use a paint pen when the grout is genuinely stained through, when it has been colonised by mildew that keeps returning, or when it was never sealed and has absorbed years of grime. No amount of scrubbing brings that back. The pen covers rather than cleans. Both Rainbow Chalk pens here are non-toxic, water-based, and the listing states 150 ft of coverage per pen on 2mm grout.

The clue is a small test. Put any grout whitener liquid on a hidden line, wait the dwell time, and rinse. If it comes back three shades brighter, buy the liquid. If it barely shifts, buy the pen.

What one 32 fl oz bottle really covers

Coverage is the specification the listings underplay. Three of these bottles hold 32 fl oz. The APULITO gel holds 10 fl oz. The pens carry 7 mL each. That is not a like-for-like comparison, and the maths matters.

• A 32 fl oz spray of the Zep Foaming Miracle, used for weekly maintenance on a standard shower and bathroom floor, is a multi-month bottle.
• The same 32 fl oz of Zep Cleaner and Brightener, used as a one-time restoration on a full ceramic floor, may be a single-project bottle.
• The 10 fl oz APULITO gel, applied thickly to vertical shower grout, is enough for one enclosure done once.
• Each Grout Pen claims 150 ft of 2mm grout coverage. A small bathroom floor of 4-inch tiles has roughly that in a single room.

The point: match the volume to the project. Buying the 32 fl oz Zep for a backsplash is overkill. Buying a single grout pen for a whole kitchen floor is not enough.

Best grout whitener product picks

1. Zep Grout Cleaner and Brightener — Best overall

Zep's acidic 32 fl oz formula is the strongest liquid restorer in the set and the right default for white grout on ceramic tile.

Best for: reviving dingy white grout on ceramic floors with an acidic deep-clean Skip it if: your tile or stone reacts to acid, or grout is stained beyond cleaning

Zep sits in the entry price band and is the second-cheapest of the six, which is unusual for the strongest-format cleaner in a shortlist. The listing describes an acidic formula that restores stained grout lines without heavy scrubbing, with a stated 3-minute dwell before wiping. The bottle weighs 2 lb at 9.88 x 6 x 3.5 in, and Zep publishes a warranty on the product page. The model is ZU104632.

The trade-off is exactly what makes it effective. Acidic cleaners are not friends with marble, travertine, limestone or unsealed natural stone. Zep says the formula suits white and colored grout, and it lists ceramic and porcelain tile as the substrates. Read that as a boundary, not a soft warning. Anyone with a stone floor should skip straight to the Black Diamond pick.

Against the Foaming Miracle sibling, this one goes harder and is meant for restoration rather than upkeep. Zep's own listing suggests using them in sequence, brightener first, then the maintenance foam.

Pros:

• Second-cheapest of the six
• Short 3-minute dwell claim
• Suitable for white and colored grout
• Published warranty on the listing
• Sells faster than most of this set

Cons:

• Acidic, so unsafe on marble, travertine and other stones
• Will not fix grout that is stained through
• Not a fit for daily maintenance

2. Zep HomePro Foaming Miracle Grout Cleaner & Protectant — Best budget pick

The cheapest pick here and the one to keep under the sink for weekly upkeep on grout you have already restored.

Best for: weekly maintenance on already-clean grout across ceramic, porcelain and stone Skip it if: you need to lift years of ground-in bathroom staining in one pass

This 32 fl oz foaming spray is the cheapest of the six and the one buyers of this set choose most often. Zep pitches it as a one-step clean-and-protect, using what the brand calls XtraGuard Technology to form an invisible barrier after each use. The listing says it suits ceramic and porcelain tile, granite and quartz, and it works on both tinted and white grout. The Mountain Drop scent is a Zep claim, not a promise.

The 4.5 lb, 11.2 x 4.5 x 3 in bottle is heavier than the Cleaner and Brightener, which points to a foaming trigger head rather than a pour cap. That matters on vertical shower walls, where the foam clings long enough to work.

The honest weakness: this is a maintainer, not a restorer. Zep's own listing recommends the acidic Cleaner and Brightener first for stubborn stains, then this foam to hold the line. Use it alone on decades-old grout and you will be disappointed.

Pros:

• Cheapest of the six
• Foaming format clings to vertical grout
• Works on ceramic, porcelain, granite and quartz
• Explicit protectant claim after cleaning
• Sells faster than the rest of this set

Cons:

• Not built for heavy stain restoration
• Protectant claim is not independently verified
• Scent is a matter of taste

3. Black Diamond Stoneworks Ultimate Grout Cleaner — Most versatile

The only listing in this set that states acid-free compatibility with marble, granite, travertine and coloured grout.

Best for: marble, travertine and coloured grout where acid is not an option Skip it if: you specifically want a strong acidic strip on white grout

Black Diamond sits in the premium price band and is the most expensive liquid of the six, but the reason is on the label. Its 32 fl oz formula is described as acid-free, so it will not etch marble, granite, travertine, ceramic or coloured grout. Nothing else in this set makes that specific claim across that specific range of substrates. If you have a stone bathroom, this is the only pick here that fits, full stop.

The bottle weighs 2.25 lb and the listing suggests a 13-minute dwell before agitating with a brush and rinsing. That is a longer wait than the 3 minutes Zep quotes, which is the trade-off you accept for losing the acid.

Against the two Zeps, Black Diamond is not going to strip years of ingrained staining in a single pass. It removes dirt, grease, soap scum and oils, which is a fair claim, but a decades-old ceramic floor may still need the acidic route. This is the versatile pick, not the strongest.

Pros:

• Acid-free, safe on marble and travertine
• Suitable for coloured grout
• Comes with a brush per the listing
• 13-minute dwell allows proper penetration

Cons:

• The most expensive liquid in this set
• Slower dwell than the acidic option
• Not the best pick for deep restoration on white grout

4. APULITO Household Cleaner Gel — Best upgrade

A cling gel that trades speed for a long dwell, meant for vertical shower grout that regular sprays run off.

Best for: vertical shower grout where a gel needs to cling for hours without dripping Skip it if: you want the job done in a single afternoon

APULITO takes a different route to grout whitening: a 10 fl oz gel that stays where you put it. The listing states a 3–5 hour dwell for routine areas and up to 10 hours for severe staining, with no scrubbing required at rinse. That is a genuinely different approach to the two Zep liquids, which are wipe-and-go, and it is the reason this is the upgrade pick rather than another all-rounder.

The listing describes it as suitable for tile, walls, bathtubs and silicone sealant around windows, sinks and baths. Silicone is the interesting one. Discoloured shower silicone is a job most cleaners duck, and this listing does not.

The trade-offs are real. It is the slowest-selling of the six, and the specification sheet is thin: no weight, no dimensions, no warranty listed. You are buying the format and the dwell time on trust. The 10 fl oz bottle also does not stretch across a whole house. This is a one-enclosure product.

Pros:

• Gel format clings to vertical grout
• Long dwell claim, up to 10 hours on stubborn stains
• Listing mentions silicone sealant specifically
• No scrubbing claim at rinse

Cons:

• Smaller 10 fl oz bottle than the liquids
• Sparse published specifications on the listing
• The slowest-moving pick of the six
• Long dwell means the room is out of use

5. Rainbow Chalk Markers Grout Pen 2-Pack — Best lightweight

Two 7 mL pens with a 5mm tip, the right entry into the pen route for a single bathroom or backsplash.

Best for: small bathrooms or backsplashes where the grout is past cleaning Skip it if: you have wide floor grout lines running through a whole kitchen

This 2-pack of Grout Pens is the practical starting point when a liquid whitener will not shift the stain. Each pen carries 7 mL of what Rainbow Chalk describes as a non-toxic, water-based colorant, with a stated coverage of 150 ft on thin 2mm grout. The tips are 5mm and the pack weighs 25 g at 7.48 x 3.74 x 0.55 in.

The difference between this and the 3-pack sibling is one pen. That is the whole story on paper, and the coverage difference matters more than the price gap. Two pens cover a small bathroom floor or a decent backsplash. A whole kitchen needs three, or a spare in reserve for touch-ups a year later.

The honest weakness of any pen: it is paint, not cleaning. Grease and mildew have to be scrubbed off before you paint over them, otherwise the pigment sits on top of dirt and lifts within weeks. Rainbow Chalk suggests a small test area first, which is fair advice given cap colour does not exactly match the ink shade.

Pros:

• 150 ft coverage claim per pen
• 5mm tip suits 2mm grout lines
• Non-toxic water-based formula per the listing
• Skips the scrubbing route entirely for stained-through grout

Cons:

• Two pens will not do a whole kitchen floor
• Requires a clean, dry surface to bond
• Cap colour is not the exact ink shade
• Slower to sell than the liquids in this set

6. Rainbow Chalk Markers Grout Pen 3-Pack — Best premium

The 3-pack is the pen buy for a whole-bathroom project, with one pen held back for touch-ups.

Best for: whole-bathroom grout repainting projects with a spare pen in reserve Skip it if: you only need to touch up a metre of backsplash

This is the same pen as pick 5, sold three to a pack instead of two. Each pen holds 7 mL with a 5mm tip and the same 150 ft coverage claim on 2mm grout. Total pack weight is 2.65 oz, and the dimensions are identical to the smaller pack. Model number GP81108/3.

The choice between the two Rainbow Chalk packs is arithmetic, not preference. A single pen carries roughly 150 ft. A standard bathroom floor with 4-inch tiles has, very roughly, in that region. Adding a shower wall pushes past a single pen. Adding a whole bathroom floor plus shower walls plus a tub surround pushes past two. That is where the 3-pack earns the price gap.

This sits in the premium price band and is the most expensive pick of the six, which makes it a considered buy rather than an impulse one. It is also the slowest-selling pen of the two. The trade-off is stock in reserve. Grout lines darken at different rates around the room, and a pen that dries out on the shelf a year later is money wasted, so the buyer of a 3-pack is really buying insurance on year two.

Pros:

• Three pens cover a whole bathroom, floor, walls and tub surround
• Spare pen for touch-ups a year later
• Same 5mm tip and non-toxic formula as the 2-pack
• Non-toxic water-based formula per the listing

Cons:

• The most expensive pick in this set
• Overkill for a backsplash or a small floor alone
• Pens can dry if stored badly between uses
• Cap colour is not the exact ink shade

How to apply a grout whitener without wrecking the tile

Nothing on any listing prepares a buyer for the first mistake. Here is the safe route.

1. Test in a hidden spot. Every acidic cleaner risks etching. Every pen risks looking wrong against the tile. Ten minutes now saves the floor.
2. Dry the grout first, especially for the APULITO gel. Water dilutes the formula and shortens the dwell.
3. Ventilate. Acidic and gel formulas both need airflow. Open the window before the bottle.
4. Respect the dwell time. Zep says 3 minutes, Black Diamond says 13, APULITO says up to 10 hours. Rinsing early means doing it again.
5. Rinse thoroughly. Residue attracts dirt and undoes the work.
6. For pens: clean first, dry completely, then paint. Two thin coats hold better than one thick one.

The single biggest error is using acid on natural stone. Etching is permanent. If the tile is marble, travertine, limestone or any polished stone, the only pick in this shortlist that fits is the Black Diamond, and even then a test patch matters.

What the listings do not tell you about whitening

Grout whitening has three permanent unknowns the product page will not answer:

• Sealing. New grout is sealed, old grout usually is not. Sealed grout responds well to any of the liquids here because the stain sits on the surface. Unsealed grout has absorbed the stain, and no amount of cleaner brings it fully back. This is when a pen wins.
• Colour match. The Rainbow Chalk pens come in white. Grout is rarely truly white. It runs off-white, cream, grey, beige. Rainbow Chalk itself notes the cap colour is not the exact ink shade, so a test patch behind the toilet or under a rug edge is not optional.
• Longevity. Chemical whitening lasts until dirt returns, which is a function of use, sealing and ventilation, not the product. Pen coverage lasts until the pigment abrades, which in a shower floor is faster than in a bathroom wall. Neither is forever.

Buy on the assumption that grout is a maintenance job. The Zep Foaming Miracle exists because Zep knows this too.

The verdict

The best grout whitener across a mixed field is Zep's Grout Cleaner and Brightener, at 32 fl oz with a 3-minute dwell and stated compatibility with white and colored grout. It sits in the entry price band as the second-cheapest of the six, which is where you want the strongest liquid to be. If your grout is stained through rather than dirty, pivot to the Rainbow Chalk Markers Grout Pen 3-pack: three 7 mL pens with a 5mm tip and 150 ft of coverage each, enough for a full bathroom project.

Two conditions flip the recommendation, and they are non-negotiable.

• If the tile is marble, travertine, limestone or any polished natural stone, buy the Black Diamond acid-free formula instead. Acid etches stone. Do not gamble.
• If the job is vertical shower grout with heavy staining, the APULITO gel and its 3–10 hour dwell will hold on the wall in ways a wipe-off spray cannot.

Everyone else, buy the Zep. Then buy the Zep Foaming Miracle for the following week. The two together are the real answer.

FAQ

Is a grout whitener worth it compared with replacing the grout?

A grout whitener is worth it in almost every case where the grout is intact. Regrouting means chiselling out old lines, mixing new grout, sealing it, and losing a bathroom for two days. A 32 fl oz bottle of Zep or a pack of Grout Pens costs a fraction of that in time. Only replace grout when it is cracked, missing, or has failed as a seal.

What is the best grout whitener for natural stone floors?

The best grout whitener for natural stone in this shortlist is Black Diamond Stoneworks Ultimate Grout Cleaner. It is the only 32 fl oz option here that states an acid-free formula and lists marble, granite, travertine and ceramic as compatible surfaces. Acidic cleaners like Zep's Cleaner and Brightener will etch polished stone permanently, so stone owners have no other pick in this set.

Grout pen or liquid cleaner: which one should I choose?

Choose a liquid cleaner when the grout was originally white and darkened over time. The colour is trapped under dirt and comes back with a good clean. Choose a grout pen, like the Rainbow Chalk 3-pack, when the staining has soaked in permanently, the grout was never sealed, or mildew keeps returning. Pens paint over the problem rather than lifting it.

How much grout can one Grout Pen actually cover?

One Grout Pen covers up to 150 ft of thin 2mm grout, according to Rainbow Chalk's listing. In practical terms, that is roughly a small bathroom floor of 4-inch tiles per pen. The 2-pack suits a bathroom or a backsplash. The 3-pack suits a whole bathroom including shower walls and tub surround, with one pen kept in reserve for touch-ups a year later.

Can Zep Cleaner and Brightener be used on coloured grout?

Zep's listing states that the Cleaner and Brightener formula suits both white and colored grout lines on tile floors. That said, coloured grout with any acidic cleaner is worth a test patch first in a hidden spot: a corner under a rug, behind the toilet, or the edge of a threshold. The 3-minute dwell time is short enough to test without much risk.

Grout is one of those jobs that looks impossible until you match the right product to the actual problem. Most bathrooms need a liquid restorer first and a maintenance spray after, which is why Zep's Cleaner and Brightener is the winner and its Foaming Miracle sibling is the smart companion buy. Start with a test patch, respect the dwell time, and rinse properly. If the grout still looks tired after a proper clean, that is when the Grout Pens earn their place. Match the format to the substrate, and the room comes back.

Last updated: September 23, 2026. Product availability re-checked.

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