Prep first
Before you start
- Wipe the film with a sponge dipped in cool water, then dry with a clean, soft cloth.
- Rub a damp cloth dusted with baking soda over the film on tile, grout, fiberglass or acrylic.
- Rinse well afterward so no cleaner residue is left behind.
- Test any cleaner on a hidden spot first.
Soap scum in a bathtub is a film, not a spill, left when soap reacts with the calcium and magnesium in hard water. Built-up film can take a repeat of the gentle treatment, but the tub material decides how hard you can scrub. Dull or scratched acrylic and cast iron each have their own limits, and improper care can void a cast iron warranty.
Before you reach for a scouring cleanser on old soap scum, check your tub material, since some finishes can't take grit. Old film usually lifts in a few patient rounds rather than one hard scrub. If it still won't shift, stop and get a pro before you damage the finish.
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)
7 items
What you'll need
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- Baking sodaLifts the film when rubbed on a damp cloth. (opens Amazon)
- Soft sponge or clothCleans without scratching acrylic or cast iron. (opens Amazon)
- Soft-bristled brushReaches grout lines, corners and the base of fixtures. (opens Amazon)
- Clean, soft towelDries surfaces after each rinse.
- Plastic bucketHolds the diluted bleach mix if you disinfect. (opens Amazon)
- Household disinfecting bleachUsed only in the optional final step, and always diluted first. (opens Amazon)
- Protective glovesProtect your skin when you mix the bleach. (opens Amazon)
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5 steps
Step by step
Step 1 of 5
Clear the tub and rinse it
Take shampoo bottles, soap dishes, bath toys and anything else out of the tub and shower. Rinse every surface with warm water to loosen dirt and debris before you start scrubbing.
Step 2 of 5
Rub the film with baking soda
Sprinkle baking soda on a damp sponge or cloth and rub it over the film on the tub walls, tile and fixtures. Work one section at a time so the film is loosened before you move on.
Careful. Keep baking soda off aluminum and don't scrub flat or matte painted walls hard.
Step 3 of 5
Scrub the tub, grout and fixtures
Use a sponge or brush to scrub the tub, shower walls, grout lines and fixtures. Give extra time to the spots where the scum is most visible.
Tip. A small brush reaches grout lines and the base of the faucet more easily than a sponge.
Step 4 of 5
Rinse and dry every surface
Rinse the baking soda and loosened film off every surface with clean water. Wipe the tub dry with a clean, soft cloth so no residue is left behind.
Tip. Rinse the sponge often so you aren't spreading the film back onto clean spots.
Careful. Don't let any cleaner soak on the surface or dry before you rinse it off, and rinse overspray off nearby surfaces.
Step 5 of 56 minutes
Disinfect with diluted bleach last
If you want to disinfect, mix 1/3 cup household disinfecting bleach into 1 gallon of cool water in a plastic bucket, wearing gloves and protective clothing. Apply it to the tub, shower walls and grout, keeping it off the faucet and other fixtures, and let it contact those surfaces for 6 minutes.
Then refill the bucket with clean water, use it to rinse the areas the showerhead won't reach, and let everything air dry.
Tip. If your tub isn't acrylic, a ready-to-use bleach foam can replace the mix: spray it 4-6 inches from the surface until thoroughly wet, let it stand for 5 minutes, then rinse or wipe clean.
Careful. Never mix bleach with vinegar, ammonia, toilet bowl cleaners or acidic scale removers, and never use it at full strength.
If you'd rather buy than mix
Best products for soap scum on bathtubs
If you'd rather skip bleach, use a bleach-free disinfecting bathroom cleaner in place of the bleach mix and follow its label.
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.
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 tub is finished when the surface looks clear and feels smooth once it's dry. If a dull haze stays after drying, the film is still there, so repeat the baking soda rub before you move on.
What changes for yours
Adjust for your bathtubs
Removing from a bathtub
Most of what changes on a bathtub depends on the material, so identify it before you scrub. If you can't tell, use only the baking soda and clear water until you know.
The rest of the steps stay the same whatever the material, since the film responds to the same rub and rinse.
Acrylic tub
Acrylic tubs can't take abrasive cleansers or solvents, so keep the scrubbing to a soft sponge. Baking soda and clear water are the gentlest options and the ones to reach for first.
Airjet acrylic baths also can't take ammonia, so keep that cleaner out of the room entirely.
Cast iron tub
Cast iron needs no steel wool, wire brushes, abrasive pads or solvents, so the soft sponge and baking soda do the work. The only exception is a sparing abrasive cleaner on stubborn spots, and it must be used with water.
Keep the bleach mix off any bare or rusty patches as well, and rinse it away completely before the surface dries.
Vitreous china tub
Vitreous china scratches and dulls under strong abrasive cleaners, so keep the scrubbing gentle and skip them. Ammonia cleaners can damage its finish, so leave those out too.
The baking soda rub and clear-water rinse are the safe default on this material.
Heavy or long-standing buildup
Old soap scum has had time to bond to the surface, so one pass often isn't enough. Repeat the baking soda rub on a damp cloth over each section, then rinse with clear water and dry.
Dried film on cast iron can take a sparing rub with an abrasive cleaner, used with water and never with steel wool or pads. On acrylic and vitreous china, stick to the baking soda, since abrasive cleansers will scratch and dull the finish.
If the film still won't lift after that, stop and check what the tub is made of before trying anything else. Some old film takes several passes, and a faint haze can remain on a tub that has been coated for years.
Vinegar, baking soda, peroxide and more
Do home remedies work on soap scum on bathtubs?
Many home remedies get recommended for soap scum, but only a few suit a bathtub. The baking soda rub fits a bathtub best, and the rest either don't suit the surface or aren't needed.
Works1Skip4Avoid1
What makes it worse
Mistakes to avoid
Don't skip the grout and corners
Grout lines and corners are where soap scum and grime often build up, so they're easy to miss. Give them their own pass with the brush during the scrubbing step.
Don't reach for aerosol sprays on acrylic
Aerosol cleaning products are a poor fit for acrylic, so leave them on the shelf. The baking soda, sponge and clear water handle the same job without the extra risk.
When to call a professional
For dull or scratched acrylic, contact the manufacturer's customer service for repairs. Improper cleaning can void a cast iron tub's warranty, so check the terms before using anything stronger.
Questions
What is soap scum made of?
Soap scum is soap that has reacted with the calcium and magnesium in hard water. That reaction leaves a film rather than a spill, which is why it clings to tub walls and grout.
Can I use baking soda on an acrylic tub?
Yes, a damp sponge or cloth with baking soda works on acrylic, along with tile and fiberglass. Rub gently and rinse well so no residue is left behind.
Can I use the bleach mix on my faucet?
No. Don't use ammonia cleaners on PVD faucet finishes.
Bleach is off limits there too. Acid cleaners are off limits as well, so clean the faucet with baking soda and clear water.
Will soap scum keep coming back?
It can, especially with hard water, since the minerals are what turn soap into film. A water softener removes those minerals, which is the long-term fix.
Do I need to rinse before using bleach?
Yes. Everything from the earlier steps has to be rinsed away first, so the bleach is the last thing on the surface.
Is the bleach step required?
No. The bleach step is for disinfecting, so it's optional if you only want the film gone. The baking soda rub and scrub handle the soap scum itself.
Soap Scum 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.