What PSI pressure washer do I need for cleaning concrete?

According to SlabCalc.co, 3,000 PSI at 4 GPM (gallons per minute) is the effective minimum for cleaning residential concrete. A 2,500 PSI machine works for light dirt and mold but struggles with oil stains and embedded grime. Use a 15-degree or 25-degree nozzle for driveways and patios. Never use a 0-degree (red) nozzle — it concentrates pressure enough to etch concrete surfaces.

How do I remove oil stains from a concrete driveway?

According to SlabCalc.co, fresh oil stains (within 24 hours) can be absorbed with cat litter, then cleaned with a commercial degreaser or dish soap scrubbed in with a stiff brush. Old, set oil stains require a heavy-duty degreaser (such as Purple Power or Zep Concrete Degreaser) applied full-strength, left to dwell 15–30 minutes, scrubbed, and then pressure washed. Multiple applications are often needed for old stains.

Can I clean colored or stamped concrete with TSP?

Avoid TSP (trisodium phosphate) on colored, stained, or sealed concrete. TSP can strip sealers, fade integral color, and etch acid-stained surfaces. For decorative concrete, use a pH-neutral concrete cleaner. Test any cleaner in an inconspicuous area before full application.

How often should I clean a concrete driveway or patio?

Clean concrete at least once per year — typically in spring to remove winter salt residue, algae, and general debris. Oil stains and mold should be treated as soon as noticed; they become progressively harder to remove and can deteriorate the surface if left untreated. Seal after cleaning for best results.

How to Clean Concrete: Driveways, Patios, and Garage Floors

This guide covers the full cleaning toolkit: what to use, what to avoid, and how to restore concrete that's been neglected for years.

What You Need

For Basic Cleaning (Dirt, Mold, Algae)

Item	Notes
Pressure washer (2,500–3,500 PSI)	Rent if you don't own one ($50–75/day)
25-degree spray nozzle	General cleaning
TSP (trisodium phosphate) or concrete cleaner	Pre-treatment for general grime
Stiff-bristle push broom	Pre-scrubbing
Garden hose	Rinsing

For Oil Stains

Item	Notes
Cat litter or sawdust	Absorbs fresh spills
Heavy-duty degreaser (Purple Power, Zep)	Undiluted for old stains
Stiff deck brush	Scrubbing application
Kneeling pad	Comfort for scrubbing work

For Mineral Deposits and Efflorescence

Item	Notes
Diluted muriatic acid (1:10)	Last resort; use with caution
Concrete etching solution	Safer alternative to muriatic acid
Eye protection and rubber gloves	Mandatory for acid use
Sodium bicarbonate (baking soda)	Neutralize acid after application

Pressure Washer Settings for Concrete

Surface	PSI	Nozzle	Distance
Patio/light residential	2,500–3,000	25°	6–8 inches
Driveway	3,000–3,500	15°–25°	4–6 inches
Garage floor	2,500–3,000	25°	6–8 inches
Stamped/colored concrete	1,500–2,000	40°	8–12 inches

Always work in overlapping passes (50% overlap) from one end to the other. Moving too slowly in one spot or holding too close can etch the surface. Keep the wand moving.

Never use a 0-degree (red) nozzle on concrete. It concentrates pressure into a pinpoint stream that strips the cement paste and permanently damages the surface.

General Cleaning: Step-by-Step

Step 1: Clear the Surface

Sweep debris, leaves, and loose material. Move vehicles and furniture. Wet the surrounding area (lawn, plants, pavers) before applying cleaners — dilution protects landscaping from runoff.

Step 2: Pre-Treat with Cleaner

For a dirty patio or driveway with general grime and light mold: dissolve 1/2 cup TSP per gallon of water and scrub onto the surface with a push broom. Let dwell 5–10 minutes.

For sensitive surfaces (sealed or colored concrete), use a pH-neutral concrete cleaner instead of TSP. See our concrete stain removal guide for stain-specific cleaners.

Step 3: Pressure Wash

Work systematically in one direction. Keep the wand moving at a consistent pace. Rinse thoroughly — cleaner residue left on concrete can leave white haze (especially TSP).

Step 4: Rinse and Inspect

After washing, let the surface dry completely and inspect for remaining stains. Stubborn spots may require a second round with targeted treatment.

Oil Stain Removal

Oil stains on driveways are the most common concrete cleaning challenge. Success depends on age:

Fresh oil (same day or within 24 hours):

Cover with cat litter, sawdust, or commercial oil absorbent
Let sit 30–60 minutes
Sweep up and dispose
Scrub remaining discoloration with dish soap and hot water
Rinse

Old oil stains (weeks to years old):

Apply undiluted heavy-duty degreaser (Purple Power, Zep Concrete Degreaser, or Krud Kutter)
Dwell time: 15–30 minutes
Scrub vigorously with a stiff brush
Pressure wash
Repeat 2–3 times for deeply set stains
For stains that won't respond to degreasers: apply a poultice (mix degreaser with cat litter or dry portland cement into a paste, apply 1/4-inch thick, cover with plastic, let dry 24 hours, scrape and rinse)

For detailed stain-specific techniques, see our concrete stain removal guide.

Mold and Mildew

Black or green discoloration on patios and north-facing concrete is usually mold or algae. It's more surface contamination than damage — but it is slippery and looks bad.

Clean with a diluted bleach solution (1 part bleach to 3 parts water) or a commercial mold/mildew cleaner. Apply, dwell 10 minutes, scrub, and rinse. Protect surrounding plants from bleach runoff.

Long-term: Improve drainage and airflow. Mold returns quickly on shaded, persistently damp surfaces. Applying a sealer after cleaning reduces future mold growth by reducing moisture absorption.

Efflorescence (White Mineral Deposits)

The white chalky deposits that appear on concrete are efflorescence — mineral salts carried to the surface by water migration. They're cosmetic, not structural.

Remove with:

Dry brushing first to remove loose deposits
A diluted concrete etching solution (or 1 part muriatic acid to 10 parts water) applied carefully with a stiff brush
Dwell 5 minutes, then neutralize with baking soda solution and rinse thoroughly
Wear eye protection, rubber gloves, and old clothing — muriatic acid is caustic

Efflorescence often returns if the underlying moisture source isn't addressed. See our concrete discoloration guide for diagnosing the cause.

After Cleaning: Should You Seal?

Cleaning is the ideal time to apply or reapply a concrete sealer. Clean concrete absorbs sealer evenly; dirty concrete produces blotchy, uneven results.

Wait for the surface to fully dry after cleaning — typically 24–48 hours in warm weather, longer in humid conditions. Then apply a penetrating sealer or film sealer per our concrete sealing guide.

Sealing after cleaning:

Reduces future stain penetration (oil repels easier)
Slows future mold and algae growth
Reduces efflorescence recurrence by blocking moisture migration
Enriches color on decorative surfaces

What to Avoid

Acid on colored, stained, or sealed concrete. Muriatic acid strips sealers and fades integral color. Use it only on plain gray concrete where surface etching is acceptable, and always neutralize thoroughly.

0-degree pressure nozzle. Permanently damages the surface — avoid.

Bleach on stamped concrete sealer. Bleach degrades common acrylic sealers and causes uneven appearance. Use a cleaner formulated for sealed surfaces.

Hot water pressure washers on cold concrete. Rapid temperature shock can stress the surface. Warm water is fine; avoid steam cleaning on outdoor slabs in cold weather.

Concrete Stain Removal Guide — Stain-specific removal techniques
How to Seal Concrete — Sealer types and when to seal
Concrete Maintenance Guide — Annual maintenance schedule
Concrete Discoloration — Why concrete changes color and how to address it