Prep first
Before you start
- Rinse a fresh splash with plenty of plain water.
- Wear goggles and gloves and work in fresh air when handling pool chemicals.
- If you need to dissolve a pool chemical, add the chemical to the water, never the water to the chemical.
Chlorine that lands on a concrete patio or pool deck usually bleaches the color out, so what you're left with is a lighter patch rather than a stain you can wash off. Once that color is gone it rarely returns, which means the realistic goal is clearing away the grime around the spot and judging the result only after the concrete has fully dried. Wet concrete always looks darker, so it's easy to misread a faded area while it's still damp.
For chlorine stains on concrete, start with plain water and a stiff brush. Stamped, sealed or painted concrete needs a lighter touch, so check the surface before you use anything strong. If the spot is old, scrub it with a mild detergent and a stiff bristle brush, and call a pro if the lighter patch doesn't change.
Before you start
What concrete, brick & driveways can take
Safe to use3
- Water
- Hot water
- Soaking
Use with care5
- Chlorine bleach
- Oxygen bleach
- Solvents (alcohol, spot removers)
- Acids (vinegar, lemon)
- Scrubbing and abrasives
7 items
What you'll need
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- Stiff fiber brushFor dry-brushing loose grit off the surface. (opens Amazon)
- Stiff bristle brushFor scrubbing the spot in the cleaning step. (opens Amazon)
- Mild detergent or kitchen cleanserFor the scrub step. (opens Amazon)
- Hose or bucket of plain waterTo rinse and keep the concrete wet while you work.
- GogglesFor handling any pool chemicals. (opens Amazon)
- Gloves (opens Amazon)
- Pressure washer (optional)Only if the spot still shows after scrubbing, at 400 psi or less. (opens Amazon)
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6 steps
Step by step
Step 1 of 6
Rinse a fresh splash first
If chlorine has just splashed onto the concrete, rinse the spot with plenty of plain water right away. The sooner it's flushed, the less time the chlorine has to work on the surface.
Careful. Never add acid or vinegar to chlorine, and never mix pool chemicals with each other; toxic gas can form.
Step 2 of 6
Test a hidden corner
Choose the gentlest cleaning method that could work, and try it on a small spot out of sight first. Look at the result once the test spot has dried, and only move on if it's clean and the concrete looks the same.
Step 3 of 6
Soak the concrete with water
Saturate the spot and the concrete around it with water before any cleaner touches it. Keep it wet while you work so the cleaner doesn't soak in unevenly.
Step 4 of 6
Dry-brush the loose grit
Dry-brush the spot with a stiff fiber brush to lift loose grit and dirt. If the grit stays put, add water and brush again.
Step 5 of 6
Scrub, then rinse thoroughly
Scrub the spot with a mild detergent or kitchen cleanser and a stiff bristle brush. Rinse thoroughly with water so no cleaner is left drying on the concrete.
Tip. Work one small section at a time so the rest stays wet.
Step 6 of 6
Pressure wash only if needed
If the spot still shows after scrubbing, a pressure washer can help. Stay at or below 400 psi, with a 25 to 50 degree fan tip held at least 12 inches from the surface.
If you'd rather buy than mix
Best products for chlorine on concrete, brick & driveways
Look for a masonry cleaner labeled for the specific stain, and follow the label exactly. A stiff fiber brush and a mild detergent handle most of the rest.
Dawn Ultra Dish Soap Refill Jug
These are the everyday supplies the steps above use, in the versions most people buy on Amazon.
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 grime around the patch should lift with each scrub, and the edge of the faded area should blend in as you go. Judge the result only when the concrete is bone dry, and if the patch looks the same after a couple of rounds, the lost color is probably permanent and the old-marks section below explains your options.
What changes for yours
Adjust for your concrete, brick & driveways
Pool deck
A pool deck gets the most splashes, so the rinse comes first every time. Work the faded spot first, then clean the rest of the deck so the wet edges don't dry out in the sun.
Blue-green marks there are a separate problem, usually copper, so scrubbing won't clear them the way it clears a chlorine spot.
Driveway
A driveway collects more grime and tire film than a patio, so the detergent scrub does more of the work. Wet one section at a time so the concrete stays damp while you scrub.
Test a corner near the edge first, then do the rest of the slab in sections.
Garage floor
Garage floors pick up oil and grime along with any chlorine splash, so the mark may look darker than it is. If the spot is oily, a commercial oil remover made for concrete is the product type to use, following its label.
Sweep out loose grit before you brush so it doesn't get worked into the surface.
Stamped or sealed concrete
If the concrete has a sealer or a stamped pattern, you may not know how it will react to a cleaner. Test the method in a hidden spot before you scrub the visible one.
If you can't find out what finish is on it, stick to water and a mild detergent and call a professional before going further.
Painted concrete
Paint can't take much scrubbing, so use the softest brush that works and the mildest cleaner first. Oxygen-based cleaners are a poor fit for painted surfaces.
Keep the pressure washer off painted concrete, since force can damage the coating.
Heavy or long-standing buildup
An older stain that has built up over time needs more than scrubbing. For a deep, localized one, make a poultice from talc, whiting, fuller's earth, diatomaceous earth or clay, mixed with the right solvent. Stronger methods carry more risk to the concrete, so start with the least aggressive option.
Spread the poultice at least 1/8 inch thick and cover it with plastic for 24 hours. Let it dry, then scrape or brush it off, and repeat as needed.
If the spot is still there, a masonry cleaner made for that stain, used exactly as its label says, is the next choice. Expect the faded color to stay even after the grime lifts.
Vinegar, baking soda, peroxide and more
Do home remedies work on chlorine on concrete, brick & driveways?
Plenty of kitchen and laundry remedies get passed around for chlorine marks, but most are built for fabric or other surfaces. Here's how each one stacks up for concrete.
Skip6
What makes it worse
Mistakes to avoid
Don't mix your own cleaner
Homemade chemical mixes can leave a stain harder to remove, and an unidentified spot treated with strong chemicals can get worse. Use a masonry cleaner made for that stain, or send a sample to a testing lab if you can't identify it.
Don't judge the spot while it's wet
Concrete looks darker and more uniform when it's wet, so a clean-looking spot can change as it dries. Wait until it's fully dry before you decide whether to go over it again.
Don't add more chlorine to it
Piling more chlorine onto a faded patch won't put the color back. Stick to water and a mild detergent for the cleanup instead.
Don't scrub before you rinse
A fresh splash should be flushed with plenty of plain water first, because scrubbing a chemical into dry grit only spreads it. Finish the rinse, then move to the brush.
Don't try to neutralize the spot
Adding ammonia or vinegar to chlorine to cancel it out creates a dangerous mix, and it doesn't fix the color. Stick to rinsing, a test patch and a stiff brush.
When to call a professional
A specialist is worth calling if the faded patch is large and hasn't improved after the gentle steps, since they can judge how much color is really gone. When the cause is unclear, a lab can test a sample so you don't gamble on a harsher product.
Questions
Does chlorine stain concrete?
Usually it takes color out of concrete rather than adding a stain, so the spot looks lighter than the rest. Cleaning can remove grime and film around it, but the lost color typically stays.
Why are there blue-green marks around my pool?
Those are usually dissolved copper, often from corrosive water attacking copper plumbing, rather than chlorine itself. Check the water and plumbing for the source, since scrubbing won't clear them the way it clears grime.
Should I dry-brush before adding water?
Yes. Dry-brushing with a stiff fiber brush lifts loose grit first, so you aren't scrubbing it around. Add water after that, then scrub the spot.
What if the spot is still there after cleaning?
Then it's likely a deeper or older mark, and the cleaning steps won't reach it fully. Move to the poultice method in the set-in section, and expect any faded color to stay.
Can I pressure wash a chlorine mark off my pool deck?
Only gently, and pressure won't bring back color that's already gone. Keep the pressure under 400 psi, use a wide nozzle angled between 25 and 50 degrees, and stand at least a foot back. Pressure only removes the grime around the patch, so judge the result once the concrete has dried.
Why does soaking the concrete first matter for a chlorine mark?
Pre-wetting keeps the masonry from soaking up the cleaner, and it keeps the loosened grime on the surface where a rinse can carry it off. Saturate the area and the concrete beneath it, then add the cleaner while it's still wet. Don't let the cleaner dry out before your final rinse.
Can I use bleach to lift a chlorine mark on concrete?
No, not for this problem. Bleach is listed for moss, algae and similar growth, and adding more chlorine to a spot that has already lost its color won't restore it. Never mix it with ammonia or acid, because those combinations give off toxic gas.
Chlorine on other materials
Other stains on concrete, brick & driveways
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.