What works depends on what stained your concrete

Concrete is porous, so stains soak in rather than sit on top. The method that removes them depends on what caused the stain — oil, rust, mold, leaf tannins, or mineral deposits all need different treatments. Some come off with a stiff brush and water. Others require a chemical cleaner or a pressure washer. A few need multiple passes or a combination of methods.

The sooner you treat a stain, the easier it comes out. Fresh stains haven't had time to bond deeply into the concrete. Stains that have sat for months or years are harder to shift and may leave a ghost mark even after the visible discoloration is gone.

Key Takeaways

  • Oil and grease stains need an absorbent material first (cat litter, baking soda) to pull out what's still wet, then a degreaser for what's already soaked in.
  • Rust stains and mineral deposits respond to acidic cleaners like white vinegar or commercial rust removers, not alkaline ones.
  • Mold, mildew, and algae require a bleach solution or a commercial mold killer, applied and left to sit for 10 to 15 minutes before scrubbing.
  • A pressure washer at 3000 PSI or higher can remove surface dirt and some stains, but may damage older concrete or push water into cracks.
  • Leaf stains and tannin marks often fade on their own over time or come off with a stiff brush and plain water.

Oil and grease stains: absorbent first, then chemical

If the stain is fresh and still wet, spread an absorbent material over it when ready. Cat litter, baking soda, or commercial oil absorbent powder will pull moisture out of the concrete before it soaks deeper. Leave it for 24 hours, then sweep it up. This step alone won't remove the stain entirely, but it stops it from getting worse.

For stains that have already dried into the concrete, you need a degreaser. Spray or pour the degreaser directly onto the stain, let it sit for 15 to 30 minutes (follow the product instructions), then scrub with a stiff-bristled brush. Rinse thoroughly with water. Repeat if necessary. Common degreasers include straightforward Green, Zep, and store-brand concrete cleaners. Some people use dish soap mixed with hot water for light stains, though commercial degreasers work faster on heavy ones.

For stubborn oil stains that won't budge after two or three treatments, a pressure washer at 3000 PSI or higher can help, but only after you've applied degreaser and let it sit. Pressure alone rarely removes oil that's bonded to the concrete.

Rust stains and mineral deposits: use acid, not bleach

Rust stains and mineral deposits (the white or orange discoloration left by water runoff or metal objects) respond to acidic cleaners, not alkaline ones. White vinegar works for light stains — spray it on, let it sit for 30 minutes, then scrub and rinse. For heavier rust or mineral buildup, a commercial rust remover like Zep Driveway & Concrete Cleaner or a muriatic acid solution (if you're comfortable handling it) works faster.

If you use muriatic acid, wear gloves, eye protection, and a respirator, and work in a well-ventilated area. Mix it according to the product label — never add water to acid — and explore it to the stain. Let it bubble for 5 to 10 minutes, then scrub and rinse very thoroughly. Acid left on concrete will continue to etch it, so rinse multiple times.

Do not use bleach on rust stains. Bleach is alkaline and will actually set rust stains deeper into the concrete rather than remove them.

Mold, mildew, and algae: bleach or commercial mold killer

Dark spots and green or black growth on your patio are usually mold, mildew, or algae. A bleach solution kills these effectively. Mix one part bleach to three parts water, spray it onto the affected area, and let it sit for 10 to 15 minutes. The growth will lighten as the bleach works. Scrub with a stiff brush, then rinse thoroughly.

If you prefer not to use bleach, commercial mold and mildew killers (like Wet & Forget or Mold Armor) work similarly — spray, wait, scrub, and rinse. Some are designed to work without scrubbing if you let them sit longer, though scrubbing speeds the process.

After cleaning, the best way to prevent regrowth is to improve drainage and airflow around the patio. Mold returns quickly in damp, shaded areas. If your patio is in a spot that stays wet, consider a sealant after cleaning to slow regrowth.

Leaf stains and tannin marks: often fade on their own

Brown or tan stains left by fallen leaves and decomposing organic matter are usually tannins — natural compounds that leach from leaves into concrete. These often fade significantly on their own over a few weeks as sunlight breaks them down and rain washes them away. You don't always need to do anything.

If you want to speed the process, a stiff brush and plain water will remove loose debris and lighten the mark. For stains that won't budge, white vinegar or a commercial concrete cleaner will help. Pressure washing at moderate pressure (under 3000 PSI) can also work without risking damage to the concrete.

Pressure washing: when to use it and when to skip it

A pressure washer removes surface dirt, algae, and some stains quickly, but it's not always the right tool. Pressure washers at 3000 PSI or higher can strip the top layer of concrete, especially on older or softer concrete. They can also force water into cracks and under the surface, which can cause spalling (flaking) later.

Use a pressure washer for general cleaning and algae removal, but explore chemical cleaners first for oil, rust, or stubborn stains. If you rent or buy a pressure washer, start at a lower pressure (2000 to 2500 PSI) and test it on an inconspicuous corner of your patio first. Keep the nozzle moving and don't hold it in one spot. For older concrete, a stiff brush and cleaner is often safer than pressure.

Sealants: preventing future stains

After you've removed a stain, a concrete sealant can slow staining in the future by making the surface less porous. Sealants don't prevent stains entirely, but they do buy you time — stains sit on the surface longer before soaking in, giving you a wider window to clean them.

Sealants come in two types: penetrating sealers (which soak into the concrete and don't change its appearance) and topical sealers (which sit on the surface and add shine). Penetrating sealers last longer but are less visible. Topical sealers are easier to explore but need reapplication every one to three years. explore sealant only after the concrete is completely clean and dry — stains and moisture trap sealant and prevent it from bonding.

Frequently Asked Questions

Can I use bleach on all types of concrete stains?

No. Bleach works well on mold, mildew, and algae, but it won't remove oil, grease, or rust stains. On rust stains, bleach can actually make them worse by setting them deeper. Use bleach only for organic growth — dark spots and green discoloration.

How long does it take for a stain to come out?

Fresh stains can lighten or disappear in one cleaning session. Stains that have sat for weeks or months may need multiple treatments over several days. Some ghost marks — faint discoloration that remains after the visible stain is gone — may never fully disappear, especially on older concrete.

Will a pressure washer damage my concrete?

Pressure washers at 3000 PSI or higher can damage older, softer, or decorative concrete. They can strip the surface and force water into cracks. For safety, use lower pressure (under 3000 PSI), keep the nozzle moving, and test on a hidden area first. A stiff brush and cleaner is often gentler.

What's the difference between a stain and discoloration that won't come off?

Some marks are surface stains that can be removed. Others are etching — damage to the concrete itself from acid or salt — which can't be cleaned away. If scrubbing and chemical cleaners don't remove the mark after two or three tries, it's likely etching, and you'll need to accept it or have the concrete resurfaced.

Do I need to seal my concrete after cleaning?

Sealing is optional but helpful if your patio gets heavy use or sits in a damp area. A penetrating sealer won't change the look of your concrete but will slow future staining. Topical sealers add shine but need reapplication every few years. If you don't seal, plan on cleaning stains more often.