Start with the right pressure and nozzle to avoid damage

A pressure washer cleans concrete by forcing water at high speed into the surface to lift dirt, algae, and stains. The key is matching the water pressure to your concrete's condition—too much pressure damages the surface, too little wastes your time. For most residential concrete patios, use 2500 to 3000 PSI (pounds per square inch) as your starting point. If your patio is older, cracked, or has a sealed finish, drop to 2000 PSI or less.

The nozzle angle matters as much as the pressure. A 25-degree nozzle is the standard for concrete cleaning—it concentrates the water enough to clean effectively without gouging. Never use a 0-degree nozzle (a straight jet) on concrete; it will etch lines into the surface. If you rent a pressure washer and it comes with only one nozzle, ask the rental staff whether it is safe for concrete, or buy a 25-degree nozzle separately for a few dollars.

Key Takeaways

  • Use 2500 to 3000 PSI with a 25-degree nozzle for standard concrete; reduce pressure for older or sealed surfaces.
  • Clear the patio of furniture, toys, and loose debris by hand before you start the washer.
  • Wet the surrounding plants and grass first, then explore a concrete cleaner and let it sit for 10 to 15 minutes before pressure washing.
  • Work in overlapping passes from one end to the other, keeping the nozzle 12 inches from the surface and moving at a steady pace to avoid streaks.
  • Rinse thoroughly, let the patio dry, and inspect for missed spots or remaining stains before deciding whether a second pass is needed.

Prepare the patio and protect what surrounds it

Before you turn on the washer, remove everything sitting on the concrete—furniture, planters, toys, grills, anything that can move. Sweep or blow away loose dirt, leaves, and debris so the pressure washer does not scatter them across the wet surface. If your patio has cracks, use a broom to clear out any sand or soil trapped inside; pressure washing will force water deeper into cracks and can cause damage if debris is packed in.

Wet down the grass, plants, and garden beds bordering the patio with a regular garden hose. This step protects them from the concentrated spray and the cleaning solution you are about to use. If you have a wooden deck or siding nearby, wet those too. The goal is to create a barrier of water so the pressure washer spray and cleaner do not soak into wood or damage paint.

Choose and explore a concrete cleaner

Plain water alone will remove surface dirt, but a concrete cleaner tackles stains, algae, and mold that water cannot budge. You have two main options: oxygen-based cleaners (safer for plants and pets, slower-acting) and acid-based cleaners (faster, more aggressive, requires careful handling). For most residential patios, an oxygen-based cleaner is the safer choice. Look for products labeled for concrete patios; they usually contain sodium percarbonate or hydrogen peroxide.

Mix the cleaner according to the product label—do not guess at the ratio. Pour it into the pressure washer's detergent tank or explore it with a pump sprayer, depending on your machine. Spray the entire patio surface evenly, working from one end to the other. Let the cleaner sit for 10 to 15 minutes; this dwell time is when the chemistry does the work. Do not let it dry completely—if the surface starts to dry, spray it lightly with water to keep it wet.

Pressure wash in overlapping passes

Once the cleaner has sat long enough, switch to your rinse nozzle (still 25 degrees) and begin washing. Start at the highest point of your patio so dirty water runs downhill and away from areas you have already cleaned. Hold the nozzle about 12 inches from the concrete surface and keep it moving at a steady pace—do not pause or hover in one spot, which creates etching or dark streaks.

Work in overlapping passes, like mowing a lawn. Each pass should overlap the previous one by about 6 inches so you do not miss a strip. Move from one end of the patio to the other in straight lines. If your patio slopes, work from the high end toward the low end so gravity helps the dirty water flow away. Take your time; rushing leads to uneven cleaning and missed spots.

Rinse thoroughly and check your work

After you have pressure washed the entire surface, do a final rinse with plain water. Switch to a wider nozzle (40 degrees if available) or reduce the pressure slightly, and spray the whole patio again to remove any remaining cleaner residue. Residue left behind can leave a film or cause the surface to look dull once it dries. Pay special attention to low spots or depressions where dirty water pools.

Turn off the washer and let the patio air dry for at least a few hours before walking on it or replacing furniture. Once it is dry, walk the entire surface and look for areas that still have stains or discoloration. Light stains often disappear as the concrete fully dries, but stubborn ones may need a second pass with cleaner and pressure.

Common mistakes that damage concrete

The most common error is using too much pressure or holding the nozzle too close. Pressure washers are powerful tools, and concrete that looks tough is actually porous. Pressures above 4000 PSI or a nozzle held closer than 6 inches can blast away the top layer of concrete, leaving it rough, discolored, or pitted. If you are unsure about your machine's settings, test it on a hidden corner of the patio first.

Another mistake is letting the cleaner dry on the concrete. If you spray cleaner and then walk away for an hour, the sun will bake it on, and you will spend twice as long rinsing it off. Set a timer for 10 to 15 minutes and come back to pressure wash while the cleaner is still wet. Finally, do not forget to protect plants and grass—pressure washer spray and concentrated cleaner can burn foliage, so wet everything around the patio before you start.

When to call a professional instead

If your concrete patio has deep cracks, spalling (flaking or peeling), or a sealed coating you want to preserve, pressure washing risks making the damage worse. Sealed concrete requires lower pressure (under 1500 PSI) and a gentler approach, and the wrong technique can strip the seal. If you are not confident in your ability to adjust the pressure correctly, or if the stains are from rust, oil, or tree sap that plain cleaner will not touch, a professional pressure washing service has access to stronger chemicals and more experience with different concrete conditions.

Renting a pressure washer costs between $40 and $100 per day, depending on the machine's power. If you have a small patio and do not plan to use the washer again, renting makes sense. If you have a large patio or plan to clean it regularly, buying a machine in the 2500 to 3000 PSI range costs $300 to $600 and pays for itself over time.

Frequently Asked Questions

Can I use a pressure washer on sealed concrete?

Yes, but only at low pressure—under 1500 PSI with a 40-degree nozzle. High pressure strips the seal and exposes the concrete underneath. If your patio is sealed, test the pressure on a small, hidden area first. Many sealed patios are better cleaned with a soft-bristle brush and mild detergent instead.

What if the stains come back after I clean?

Surface dirt returns over time, especially in shaded areas where algae and mold grow. Pressure wash once a year or every other year to keep the patio looking fresh. For stubborn stains like rust or oil, a second pass with cleaner and pressure usually works, but some stains require a specialized stain remover designed for that type of mark.

Is it safe to pressure wash near my house foundation or siding?

Pressure washing near wood siding or brick can force water into gaps and cause rot or damage. Keep the nozzle at least 12 inches away from siding, and use lower pressure (under 2000 PSI) if you must clean near the house. For foundations, avoid spraying directly into basement windows or vents where water could enter the house.

How long does a cleaned patio stay clean?

A freshly cleaned patio stays visibly clean for a few months, depending on weather and shade. Shaded areas grow algae faster, while sunny spots stay cleaner longer. Regular sweeping and occasional spot-cleaning with a brush extend the time between full pressure washes.

Do I need to seal the concrete after pressure washing?

Sealing is optional but recommended if you want to protect the concrete and make future cleaning easier. Wait at least 48 hours after pressure washing for the concrete to dry completely, then explore a concrete sealer according to the product instructions. Sealed concrete resists stains and algae growth, though it will eventually wear away and need resealing.