Prep first
Before you start
- Reach for an acidic cleaner made for lime and scale.
- Check the tub material first, since acrylic and cast iron each have their own limits.
- Keep the cleaner on for only a short time, then rinse promptly with cold water.
- Don't use chlorine bleach on this stain.
Hard water scale on a bathtub is a white, chalky film that dries onto the surface and, over time, turns flaky, crumbly, and sometimes tan or brown. Because it's a mineral deposit, soap won't dissolve it, and it takes an acidic cleaner with a pH below 7 to break it down. Your tub material decides how much of that acid you can use, and a dull or scratched acrylic finish needs the manufacturer's repair service rather than more scrubbing.
Before you reach for anything strong, check your tub material, because the wrong acid can dull the finish fast. Yellow or rust-colored marks usually need a second round rather than more pressure. Once the scale is gone, rinse well and dry the tub so it looks white again.
Before you start
What bathtubs can take
Safe to use1
- Water
Use with care4
- Soaking
- Chlorine bleach
- Acids (vinegar, lemon)
- Scrubbing and abrasives
Avoid1
- Solvents (alcohol, spot removers)
5 items
What you'll need
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- Acidic toilet bowl cleaner or lime-and-scale cleanerDissolves mineral scale, which needs an acid to break down. (opens Amazon)
- Protective glovesKeeps the cleaner off your skin while you work. (opens Amazon)
- Safety glassesProtects your eyes from splashes. (opens Amazon)
- Soft cloth or spongeWipes the surface without scratching acrylic or porcelain. (opens Amazon)
- Cold running waterRinses the cleaner away promptly and thoroughly.
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6 steps
Step by step
Step 1 of 6
Check what your tub is made of
Acrylic, porcelain (vitreous china) and enameled cast iron each have their own limits, so identify yours before you pick a product. If you're not sure, check the manufacturer's care instructions and treat the tub as the most delicate material it could be.
Careful. Cast iron can't take steel wool, wire brushes or abrasive pads.
Step 2 of 6
Gear up and spot-test a hidden area
Put on protective gloves and safety glasses before you open the cleaner. Spot-test the acid cleaner on a hidden area of the tub, such as under the rim, and watch that spot for dulling before you treat the stain.
Careful. If the test spot dulls, lightens or changes color, stop and rinse it with cold water.
Step 3 of 6
Apply the acidic cleaner to the scale
Apply an acidic toilet bowl cleaner directly onto the scaled areas, especially if the surface is porcelain. Cover only the stain, and don't spread the cleaner onto nearby surfaces.
Careful. Never mix it with chlorine bleach or any other acid, because hazardous fumes can form.
Step 4 of 62 minutes
Keep the cleaner on for 2 minutes
Let the cleaner work for no longer than 2 minutes, and wipe lightly with a soft cloth or sponge where scale remains. Keep an eye on the clock, since longer contact raises the risk of damage to the finish.
Careful. Don't let the cleaner soak or dry on the surface, and rinse overspray off nearby surfaces.
Step 5 of 6
Rinse the tub thoroughly with cold water
Rinse every treated area promptly with cold water, including the edges and the drain area. Run your hand over the surface afterward, and rinse again if anything feels slick or gritty.
Step 6 of 6
Dry the tub and wash your hands
Dry the tub with a soft cloth to slow new buildup. Then wash your hands, since you handled the cleaner even with gloves on.
If you'd rather buy than mix
Best products for hard water on bathtubs
Choose an acidic toilet bowl cleaner, and skip any product that lists bleach or ammonia. Read the label for the surfaces it's safe on before you buy.
CLR Calcium, Lime & Rust Remover
Zep Concentrated Calcium, Lime and Rust Stain Remover
How we picked these: each product is made for this type of stain, its maker doesn't warn against using it on bathtubs, and its directions fit the steps above.
Finished the steps? How does it look?
Nice work. Let it dry completely and check it again in good light. Here is what done looks like:
How to tell it's really gone →A faint mark usually needs one more round, not a stronger product.
See what to do for what you're seeing →Heavy buildup usually takes more than one round.
Heavy or long-standing buildup →When to call a professional →How to tell it's working
The scale should lift off and leave the surface smooth and evenly colored, and running a hand over it should feel clean rather than gritty. If the white film or tan crust is still there after one full round, the scale has built up and needs the stronger treatment covered below.
What changes for yours
Adjust for your bathtubs
Yellow or rust-colored marks
Yellow, orange, or rust-colored marks may not lift with the acid cleaner alone, so expect a second pass. Rust stains usually need a different product, not a harder scrub.
On enameled cast iron, use only a rust remover made for enamel, and never steel wool or wire brushes. On acrylic, skip any abrasive or solvent product, and if the surface is dull or scratched, contact the manufacturer for repair.
Porcelain and acrylic finish
A tub looks white again once the scale comes off, so the acid cleaner and the rinse do most of the work. On porcelain (vitreous china), strong abrasives and ammonia cleaners will scratch and dull the glaze, so stick with the acid cleaner and a soft cloth.
On acrylic, the acid cleaner is fine when used briefly, but abrasive cleansers and solvents leave the surface dull. A dull finish that won't polish up needs the manufacturer, not a stronger product.
Thick scale and crusty deposits
Thick, crusty buildup is scale that has had time to harden, so one short round may only soften its top layer. Repeat the acid treatment in short rounds, rinsing with cold water between them, rather than letting one application sit longer.
Scale in the drain area and along the rim often holds the most, so give those spots extra attention in each round. If the deposit still doesn't break down, switch to the stronger treatment below.
Soap scum on the tub
Soap scum is a different residue from scale, so the acid cleaner won't clear it on its own. Once the scale is gone, wash the tub with mild soap and warm water to take off the soap film.
Do the scale treatment first, then the soap wash. Rinse the tub well afterward so no soap is left on the surface.
Calcium stains
Calcium stains on a tub are the same mineral scale, since hard water deposits are calcium carbonate. Treat them with the acidic cleaner, keep contact to 2 minutes, and rinse with cold water.
Calcium that has built up for a long time may need the stronger treatment, and it's worth spot-testing first on acrylic or cast iron.
Heavy or long-standing buildup
An old stain, one that has been there for months, has usually hardened into a thick crust that the first round won't fully break down. That's normal with scale, and you don't need to scrub harder.
The stronger option is to dilute the acidic cleaner with an equal part of warm water, apply it, and leave it for no longer than 2 minutes. Rinse with cold water, and if the crust is still there, repeat the round, rinsing between rounds.
Scrub lightly with an old toothbrush on porcelain only, never on acrylic or cast iron, and rinse thoroughly afterward. Be realistic: a stubborn stain may fade rather than vanish, and one that's still there after these rounds needs the manufacturer's advice or a professional.
Vinegar, baking soda, peroxide and more
Do home remedies work on hard water on bathtubs?
Most home remedies don't dissolve mineral scale, which is why an acidic lime-and-scale cleaner is the one to use. Whether a remedy works on this stain and whether your tub can take it are the two questions that matter.
Helps1Skip4Avoid2
Chemical safety
Never mix these
Some products in this guide react dangerously with each other. Use them one at a time and rinse with water in between.
Toilet bowl cleaner + Vinegar
Bleach-based toilet bowl cleaners release chlorine gas with acids like vinegar, and toilet cleaner labels say not to mix them with other chemicals.
If they mix by accident: Stop and add nothing else; leave the area for fresh air, open windows and keep children and pets away; call Poison Control at 1-800-222-1222, or 911 if anyone has trouble breathing.
What makes it worse
Mistakes to avoid
Don't use abrasive cleansers or solvents on acrylic.
Acrylic is damaged by abrasive cleansers, and solvents can dull or harm the bath surface. Aerosol cleaning products are also a poor choice for acrylic, so keep them off the tub.
Don't use full-strength bleach or ammonia on an airjet tub.
Airjet acrylic baths can be damaged by chemically active solutions, so bleach is the wrong tool for this stain. Stick with the acidic cleaner, diluted only as the stronger treatment describes.
Don't scrub porcelain with strong abrasives or ammonia.
Strong abrasive cleaners scratch and dull vitreous china, and ammonia cleaners can damage its finish. A soft cloth with the acidic cleaner is the safer choice for scale.
Don't use vinegar or acid on natural stone around the tub.
Vinegar and acid descalers etch and dull marble, and granite and other natural stone can't take them either. For a marble or natural stone surround, follow the Marble & Natural Stone guide instead.
Troubleshooting
If the stain is still there
Pick what you're seeing:
The scale is still there after one pass
Rinse thoroughly with cold water and let the surface dry before you judge it. Then repeat the application, at full strength if the label allows, keeping any single contact under 2 minutes. Don't buy a better result with a longer soak.
The faucet or shower head is crusted solid
Fill a large sandwich bag with white vinegar, submerge the fixture in it, and leave it a few hours. Remove it, clean it and dry it; if flow is still low, take the unit apart and soak the scaled pieces in vinegar. Keep vinegar away from marble and other natural stone.
A dull patch appeared where you cleaned
Stop and rinse with cold water. Acid descalers etch marble, and CLR is not recommended on granite or other natural stone; dull or scratched acrylic needs the manufacturer's customer service for repair. Tell them what product touched the surface and how long it stayed.
When to call a professional
If the tub is acrylic and has dull or scratched spots, the stain treatment won't restore it, so contact the manufacturer's customer service for repairs. On cast iron, improper cleaning can void the warranty, so check the warranty terms before using anything stronger.
Questions
What hard water stain remover should I buy for a bathtub?
Buy an acidic cleaner made for lime and scale, such as a toilet bowl cleaner. Check the label for bleach and skip any product that contains it, then test the cleaner on a hidden spot before you use it on the whole tub.
Can I use bleach on hard water stains in a tub?
No. Bleach is alkaline and isn't recommended for hard water stains, so use an acidic cleaner made for lime and scale instead.
Can I use the same cleaner on the bathroom faucet?
Not if the faucet has a PVD finish, since harsh cleaners can damage it. Avoid ammonia products there, and check the Metal, Chrome & Tools guide for the faucet's metal.
Can I use an acid cleaner on the grout around the tub?
Be careful, because cement grout can be damaged by vinegar and other acids. For grout, check the Grout guide before you treat it.
How often should I clean the tub to keep scale away?
Rinse and dry the tub after each use with a soft cloth, which slows new buildup between deeper cleanings. Use the acid treatment only when a film or deposit comes back.
Is the cleaner safe to have around children and pets?
Keep children and pets out of the bathroom while you work, since acid cleaners can irritate skin and eyes. Rinse the tub thoroughly before anyone uses it again.
Hard Water on other materials
Other stains on bathtubs
Start from the bigger picture
How we know this
Every method, amount and warning here comes from university extension services, industry bodies and product makers. We read them, check every step for unsafe combinations and changed amounts, and write it up so you can follow it.