Will a pressure washer remove algae from concrete?

We get asked all the time: Will a pressure washer remove algae from concrete? From slippery patios to green-streaked driveways, the answer’s yes — if done right. We’ve seen algae on concrete in the burbs, on backyard patios in Byron, and creeping across damp decking. Sometimes it’s a slip risk, other times just plain ugly — either way, it’s got to go.

Why Algae Loves Concrete

Concrete is like a welcome mat for algae spores — especially when it’s damp, shaded, and covered in loose debris. Once the algae cells take hold, it doesn’t take long for a full-blown takeover.

Common Aussie trouble zones:

Concrete floors around pool areas and patios
Concrete garage floors with oil stains or water pooling
Basement floors or shaded concrete driveways in VIC and NSW
Coastal slabs with high humidity and salt exposure
Outdoor surfaces under dense trees or leaf litter

Algae growth thrives in moisture-rich environments, especially when water can’t drain properly. That’s why routine patio cleaning and regular cleaning of outdoor surfaces are key.

Will High Pressure Alone Clear Algae?

Short answer? Yes — and it’s one of the most effective methods we use.

Pressure cleaning uses a high-pressure stream of water to lift algae stains and dislodge grime from the concrete surface. But here’s the catch: pressure alone won’t always kill the algae spores. So while your driveway might look clean after pressure washing, the algae might return if you don’t use a proper cleaning solution.

Benefits

Quick algae removal from large areas
Breaks up tough stains, surface dirt, and grime
Restores the appearance of concrete patios and paths
Works on a variety of surfaces — from cement floors to brick surfaces

But like any cleaning method, it’s not magic — and it has to be done right.

Tough on Algae, Easy on Concrete

Here’s our no-fuss approach to cleaning algae from concrete with a power washer:

Step 1: Clear the Area

Remove furniture, pot plants, and toys
Sweep away loose dirt and leaves with a push broom
Use a stiff brush or deck brush on dry algae patches to loosen growth

Step 2: Choose the Right Nozzle

Use a 25-degree or 40-degree nozzle for general pressure washing. A fan nozzle covers more ground and is gentler on concrete. Avoid a 0-degree nozzle unless you’re targeting very stubborn stains — it can damage delicate surfaces.

Step 3: Apply a Cleaning Solution

Pressure washing without a cleaning solution is like brushing your teeth with just water. It might look better — but spores remain. For safe and effective algae removal, use:

Oxygen bleach (safe on concrete, doesn’t harm delicate plants)
White vinegar and warm water (DIY cleaning solution)
Mild detergent or concrete detergent in your detergent tank

Let it sit for 10–15 minutes to penetrate the algae cells. Avoid chlorine bleach unless you’ve tested for bleach absorption and have runoff control — it can harm your garden and wear out your concrete over time.

Step 4: Pressure Wash from Top to Bottom

Start at the highest point (if on a slope) and move in slow, steady lines using overlapping strokes. Keep the spray nozzle 20–30cm from the surface. Watch for the appearance of algae being lifted as the water pressure does its work.

Use a cleaner attachment for wide areas or textured concrete — it keeps water controlled and maximises cleaning capacity.

Step 5: Rinse with Clean Water

Flush the area with fresh water to remove residue, dead algae spores, and chemical cleaning agents. Inspect for any stubborn stains or rust stains — you might need a commercial rust remover for those.

In Melbourne, we recently helped a client who’d tried scrubbing green algae with boiling water and a stiff-bristled brush. After three weekends of sore shoulders and no real results, they called the Window Cleaning Melbourne Crew for backup. And that’s when we got to work — with the right attachments, correct nozzle, and a proper algae cleaner in hand.

Best Cleaning Products and Solutions

Whether you go with commercial cleaners or a homemade batch, the cleaning solution matters.

Our field-tested combos:

Oxygen bleach + warm water: safe, effective, won’t damage outdoor surfaces
White vinegar + laundry detergent: a good DIY option for light algae on concrete floors
Concrete cleaning solution: pre-mixed cleaners specifically designed for algae removal

If you’re working near edible plants, look for biodegradability for plants and avoid strong chemicals.

What to Avoid When Pressure

We’ve seen a few backyard disasters that prove how important it is to know what not to do.

Don’t:

Use high pressure on delicate surfaces like painted concrete or coloured finishes
Spray too close — it’ll rough up your slab faster than a brickie’s language on smoko
Forget protective gear — algae plus concrete plus water = slippery as
Skip pre-treatment — algae with spurts will be back in weeks without it
Use chlorine bleach around organic materials — it’s a bad idea for the environment

Soft Washing vs Pressure Washing for Algae

If your concrete’s in bad condition, or if you’re dealing with algae from surfaces including render or decking, a soft wash might be safer.

Soft washing uses:

A low-pressure hose or pump sprayer
A gentle cleaning solution like vinegar or detergent
A scrub brush or soft-bristled brush to agitate the algae

It’s slower, but safer — especially on older or decorative concrete.

Should You Seal It Post-Wash?

Once you’ve removed the algae from patio slabs or concrete driveways, don’t stop there. Sealing the surface helps prevent future algae.

Benefits of sealing:

Blocks water penetration and algae spore movement
Prevents the return of surface dirt and grime
Makes future cleaning easier

Use a penetrating concrete sealer after washing and allow the surface to dry thoroughly before applying.

Best Nozzles and Attachments for Algae Removal

Tool	Best Use
25-degree nozzle	Standard surface dirt and algae
40-degree nozzle	Gentle cleaning on wide areas
Surface cleaner attachment	Efficient cleaning of driveways and patios
Detergent tank	Apply concrete detergent or algae stain remover evenly

How Often’s Enough?

For routine cleaning, once or twice a year is ideal — more often if your property sits in a shaded, moist environment.

Spring is great for prepping the surface after damp winter months. Autumn helps clean up after storms and falling leaves.