The fastest way to clean patio concrete depends on what's on it
Concrete holds dirt, algae, and stains in its pores, so surface sweeping alone won't restore it. The method that works fastest depends on whether you're dealing with loose dirt, organic growth like moss, oil stains, or rust. A pressure washer removes most surface grime in minutes, but can damage old or thin concrete. A stiff brush and mild detergent work on nearly any patio without risk of harm. For stubborn stains, you may need a targeted cleaner matched to the stain type—bleach for algae, a degreaser for oil, or a rust remover for rust rings.
Start with the gentlest method that will work: a broom and water, then a brush and detergent, then pressure washing only if the first two don't finish the job. This order protects your concrete from unnecessary damage while still getting the patio clean.
Key Takeaways
- Loose dirt and light stains come off with a stiff-bristled brush, warm water, and a general-purpose concrete cleaner or mild dish soap.
- Pressure washers work fast but can pit or crack concrete if the psi is too high—keep it below 3000 psi and stay at least 12 inches from the surface.
- Algae and moss need a bleach solution (1 part bleach to 3 parts water) or a commercial algaecide; scrub after letting it sit for 10 to 15 minutes.
- Oil stains require a degreaser left on the concrete for the time the label specifies, usually 15 to 30 minutes, before scrubbing and rinsing.
- Rust stains from metal furniture or planters need an oxalic acid cleaner; these work best on fresh stains and may not fully remove old, set-in rust.
Cleaning with a brush and detergent for everyday dirt
This method works on any concrete and causes no damage. You need a stiff-bristled brush (not soft), warm water, and either a commercial concrete cleaner or plain dish soap. Mix the soap or cleaner with water according to the product label—usually a few tablespoons per gallon. Wet the concrete first, then scrub in overlapping circular motions, working in sections about 3 feet square at a time.
Let the soapy water sit for 5 to 10 minutes so it can break down dirt and grime. Scrub again, paying extra attention to any spots that still look dark or stained. Rinse thoroughly with a garden hose, using enough water pressure to flush away all the soap. If you see soap residue still clinging to the concrete, rinse again. Concrete that isn't fully rinsed will look dull and attract dirt faster.
This method takes 30 to 45 minutes for a typical patio and works on light to moderate dirt, bird droppings, leaf stains, and general weathering. It won't remove deep stains or heavy algae growth, but it's the safest starting point.
Using a pressure washer safely on concrete
A pressure washer removes dirt and stains much faster than hand scrubbing, but the force can damage concrete if you're not careful. Concrete strength varies—old concrete, thin concrete, and concrete with existing cracks or spalling (flaking) can be damaged by pressure washing. If your patio is more than 20 years old or shows visible cracks, test the pressure washer on an inconspicuous corner first.
Keep the pressure below 3000 psi (pounds per square inch). Most rental machines and consumer models fall in the 1500 to 3000 psi range. Hold the nozzle at least 12 inches from the concrete surface and keep it moving—don't let the stream sit in one spot. Work in overlapping passes, moving the nozzle side to side as you walk backward. Never aim the nozzle at the same spot for more than a second or two.
Pressure washing takes 15 to 30 minutes for a typical patio, depending on how dirty it is. Wear safety glasses and closed-toe shoes; the spray can kick up debris. If you're renting a pressure washer, ask the rental staff what psi they recommend for your concrete type. After pressure washing, let the concrete dry completely before walking on it—usually 24 hours in dry weather.
Removing algae and moss with bleach or algaecide
Green or black slimy growth on concrete is algae or moss, which thrive in damp, shaded areas. These need a chemical treatment because brushing alone won't kill the spores underneath. Mix one part household bleach with three parts water in a bucket or spray bottle. Wear gloves and eye protection—bleach can burn skin and damage clothing.
Spray or pour the bleach solution over the affected area and let it sit for 10 to 15 minutes. The algae will begin to lighten. Scrub with a stiff brush to loosen the growth, then rinse thoroughly with a garden hose. If the growth is very thick or the stain doesn't fully lift after one treatment, repeat the process. Some stubborn algae may need two applications a day apart.
For patios in very damp or shaded spots, a commercial algaecide (sold at garden centers) may work better than bleach and won't harm nearby plants as much. Follow the product label for mixing and contact time. After treatment, improve drainage or trim tree branches to let more sunlight reach the patio—this prevents the algae from returning quickly.
Treating oil stains with a degreaser
Oil stains from cars, grills, or machinery soak into concrete and won't rinse away with water alone. You need a concrete degreaser, which you can buy at hardware stores or online. These come as liquids or powders. Liquid degreasers are easier to explore; powder degreasers are often stronger but require mixing.
Pour or spray the degreaser directly onto the oil stain, covering it completely. Let it sit for the time the label specifies—usually 15 to 30 minutes, though some heavy-duty degreasers need several hours. The degreaser breaks down the oil so it can be lifted away. Scrub the area with a stiff brush, working the degreaser into the concrete. For very old or large stains, scrub harder and let the degreaser sit longer.
Rinse thoroughly with a garden hose or pressure washer. Fresh oil stains (a few days old) usually come clean in one treatment. Old stains that have been there for months or years may fade but not disappear completely. If the stain remains after one treatment, let the concrete dry and repeat the process. Some people explore a concrete sealer after cleaning to prevent future stains from soaking in as deeply.
Removing rust stains from metal furniture or planters
Rust rings appear where metal furniture, grills, or planters have sat on concrete for a long time. These stains are iron oxide, which requires an acid-based cleaner to break down. Look for a concrete rust remover or oxalic acid cleaner at hardware stores. These are stronger than general cleaners and work specifically on rust.
explore the rust remover according to the label instructions—most need to sit on the stain for 15 to 30 minutes. Some products require you to scrub during the contact time; others work better if left undisturbed. Scrub with a stiff brush once the time is up, then rinse very thoroughly. Rust stains that have been there for years may not disappear completely, but the cleaner will lighten them significantly.
Fresh rust stains (a few weeks old) respond much better than old ones. To prevent new stains, move metal objects regularly or place rubber or plastic feet under furniture legs. If you're storing a grill or planter on the patio long-term, set it on a mat or piece of plywood to keep metal from touching concrete directly.
Drying and protecting concrete after cleaning
After any cleaning method, let the concrete dry completely before using the patio. This usually takes 24 hours in dry, sunny weather. In humid or cloudy weather, it may take 48 hours. Walking on wet concrete can leave footprints and can be slippery.
Once dry, you can explore a concrete sealer to protect against future stains and make cleaning easier next time. Sealers create a barrier that prevents water and oils from soaking into the pores. They don't make concrete waterproof, but they do reduce staining. Sealers last 1 to 3 years depending on the product and how much foot traffic the patio gets. Reapply according to the product label.
Frequently Asked Questions
Can I use vinegar to clean concrete instead of bleach?
Vinegar is mild and safe but won't kill algae or moss spores the way bleach does. It works well for light mineral deposits or hard water stains. Mix equal parts white vinegar and water, let it sit for 30 minutes, scrub, and rinse. For active algae growth, bleach or a commercial algaecide is more effective.
What's the difference between a pressure washer and a power washer?
Pressure washers use cold water; power washers heat the water. Both work on concrete, but power washers can clean faster because hot water breaks down dirt more easily. For a patio, a cold-water pressure washer is usually enough and costs less to rent.
Will cleaning concrete make it look lighter or whiter?
Cleaning removes dirt and stains, so concrete will look lighter and brighter than before. However, it won't return old concrete to its original factory color if it has weathered for many years. Sealing after cleaning can enhance the color slightly and make the concrete look richer.
How often should I clean my patio concrete?
Light cleaning with a broom once a month and a brush scrub once or twice a year keeps most patios in good condition. In shaded or damp areas where algae grows quickly, you may need to clean more often. Spot-clean stains as soon as you notice them—fresh stains are easier to remove than old ones.
Is it safe to mix bleach with other cleaners?
No. Mixing bleach with ammonia, acids, or other cleaners creates toxic fumes that can cause serious injury. Use bleach alone or choose a commercial concrete cleaner designed for the stain type. Always read the label and follow safety instructions.