Pressure washing alone won't remove oil stains, rust spots, or deep concrete discoloration. Pre-treating the surface before you wash is the step most people skip -- and it's why some driveways still look dirty after a full cleaning. Here's how to handle every major concrete stain type before the pressure washer comes out.

The Quick Answer

Match the pre-treatment to the stain type:

Oil and grease: Kitty litter to absorb excess, then commercial degreaser (15-30 min dwell)
Rust: Oxalic acid or commercial rust remover, 10-20 min dwell
Mold and algae: Diluted bleach or oxygen bleach solution, 10-15 min dwell
Efflorescence (white powder): Diluted muriatic acid or acidic concrete cleaner
General grime: Alkaline cleaner like TSP, 5-15 min dwell

In every case: apply the right cleaner, let it dwell, scrub with a stiff nylon brush, then rinse and pressure wash. Skip the pre-treatment and you're just pushing the stain around with high-pressure water. Some stains will actually set deeper if you pressure wash without treating them first.

Step 1: Clear the Surface Before Anything Else

Before you touch any chemical, sweep the concrete clear of loose debris. Use a leaf blower or broom to remove dirt, leaves, and sand, then do a quick rinse with a garden hose. Loose material clogs your nozzle, interferes with chemical contact, and makes it harder to see where the actual stains are.

This takes five minutes and makes every subsequent step work better. Don't skip it.

How to Remove Oil and Grease Stains

Oil stains are the most common complaint on driveways and garage floors. The challenge is that oil bonds with the concrete over time, and pressure washing pushes it deeper rather than lifting it out. You need to break down the oil chemically before you ever turn on the machine.

Fresh Oil Stains (Under 24 Hours Old)

Cover the stain generously with kitty litter or sawdust. Grind it into the surface with your foot and let it sit for at least 1 hour -- overnight is better for larger spills. The absorbent material soaks up the surface oil before it fully bonds with the concrete. Sweep up the kitty litter and move to the degreaser step.

Old Oil Stains

Skip the kitty litter on old stains -- the oil is already set into the pores. Go straight to a commercial degreaser or strong alkaline cleaner. Apply generously, let it sit for 15-30 minutes (don't let it dry), then scrub with a stiff nylon brush. Rinse, then pressure wash the area.

Very old or deep stains may need a second round. For severe contamination, some contractors mix a degreaser paste with an absorbent material, apply it as a poultice, let it sit 24 hours, then pressure wash. It's extra work, but it pulls up oil that a standard rinse won't touch.

How to Remove Rust Stains

Rust stains come from metal furniture, fertilizer runoff, or iron-rich water sitting on the surface. Pressure washing does nothing for rust -- you need an acid-based treatment.

Use oxalic acid or a commercial rust remover designed for concrete. Apply it to the stain and let it dwell for 10-20 minutes. You'll see the stain begin to lighten as the acid breaks down the iron oxide. Scrub with a nylon brush, rinse thoroughly, then pressure wash.

Always neutralize after any acid treatment. Mix baking soda and water and rinse the area to stop the acid from continuing to etch the concrete surface.

How to Remove Mold and Algae

Black or green staining on shaded concrete is almost always biological -- mold, algae, or lichen. Pressure washing will remove the surface layer, but the organism's roots stay in the concrete and regrow within weeks.

A diluted bleach solution (1 part bleach to 10 parts water) or an oxygen bleach solution kills the organisms at the source. Apply, let it sit 10-15 minutes, scrub, and rinse. For professional concrete cleaning jobs, sodium hypochlorite solution is the standard -- it's effective, affordable, and what most pros already have on the truck.

Keep runoff away from plant beds. Bleach-based solutions can damage landscaping if they pool near roots.

How to Remove Efflorescence

Efflorescence is the white, chalky residue that forms on concrete and masonry when water carries mineral salts to the surface and leaves them behind as it evaporates. It's not mold -- it's salt deposits -- and it needs an acidic cleaner to dissolve it.

Diluted muriatic acid (1 part acid to 10 parts water) or a commercial efflorescence remover will dissolve the deposits. Apply carefully, let it dwell for 5-10 minutes, scrub, and rinse completely. Neutralize with a baking soda rinse before pressure washing. Never let acid sit long enough to etch the concrete surface.

The Upsell Opportunity for Contractors

Pre-treatment is where smart contractors add real margin to every concrete cleaning job. Most homeowners calling for a driveway wash have no idea that oil stains, rust, or efflorescence need separate chemical treatment. When you arrive on site, assess the stains, explain what you see, and offer a stain treatment package as an add-on.

Oil stain treatment: $50-$100 per stain area
Rust removal: $75-$150 depending on coverage
Full pre-treatment package: $100-$200 for a full driveway with mixed staining

Most homeowners will say yes when you explain that standard pressure washing alone won't remove those stains. You're not padding the bill -- you're actually solving the problem they hired you for. Document the stains with before photos and show the results after. That's how you get referrals.

Bottom Line

Concrete stain removal before pressure washing is what separates a 70% clean result from a 100% clean one. Match the treatment to the stain type, let the chemistry do the work, scrub, then pressure wash. Your customers will notice the difference -- and so will your referrals.

If you're quoting driveway and concrete cleaning jobs, try QuoteSnap for free. Set your pricing for standard cleaning and add-on stain treatments so customers can see instant quotes directly on your website.

Concrete Stain Removal Before Pressure Washing (Complete Guide)