Cleaning concrete effectively starts long before you pull the trigger on a pressure washer. The real secret lies in the pre-treatment you apply to the surface. Choosing the correct solution can mean the difference between a lightly cleaned driveway and one that looks professionally restored. This guide provides the most complete, expert breakdown on what to spray on concrete before pressure washing, covering products, chemistry, scenarios, comparisons, and professional insights.

Short Answer: What to Spray on Concrete Before Pressure Washing

The best thing to spray on concrete before pressure washing is a pre-treatment solution such as a concrete detergent, degreaser, mold/mildew remover, surfactant-based cleaner, or specialty product for oil or rust. Pre-spraying is essential because it helps loosen embedded dirt, dissolve stains, and break surface tension leading to a deeper, more efficient clean with less physical effort and better final results.

Why You Should Spray a Pre-Treatment on Concrete Before Pressure Washing

How Pre-Treatment Helps Clean Concrete More Effectively

Concrete is extremely porous, meaning dirt, oil, algae, and contaminants settle deep inside the substrate. A proper pre-spray:

Softens and dissolves buildup
Breaks the bond between stains and the concrete surface
Allows water pressure to rinse away contaminants instead of merely moving them around
Reduces the need for aggressive pressure that can etch concrete

Why Skipping Pre-Spray Leads to Poor Results

Without pre-treatment:

Oil stains remain visible
Mildew and algae may return quickly
Pressure washing takes longer
Concrete may require multiple passes
Surface may be unevenly cleaned

When You Should Use Degreaser vs Detergent vs Specialty Cleaners

Detergent: Light buildup and general cleaning
Degreaser: Heavy oil, automotive leaks, garage floors
Specialty cleaners: Rust, irrigation stains, tire scuffs, mold colonies

Best Products to Spray on Concrete Before Pressure Washing (Expert Breakdown)

Concrete Detergents (General Purpose)

A balanced, all-purpose cleaner that works for dirt, dust, and light organic material. These are safe for most surfaces and ideal for routine cleaning.

Degreasers for Oil & Automotive Stains

Use a degreaser when dealing with:

Motor oil
Transmission fluid
Hydraulic stains
Grease and lubricants

Degreasers break down petroleum molecules that pressure washers alone cannot remove.

Mold & Mildew Removers

Typically sodium hypochlorite-based, these kill spores and sanitize concrete. Ideal for humid regions or shaded driveways.

Enzymatic Cleaners for Organic Stains

Best for:

Food spills
Leaf stains
Pet messes
BBQ grease
These cleaners use enzymes to digest organic material.

Specialty Rust & Mineral Deposit Pre-Sprays

Acidic formulas designed to dissolve:

Rust
Battery acid stains
Irrigation/hard water marks
Use carefully these are strong.

Eco-Friendly & Biodegradable Concrete Pre-Treatments

Best for areas with plants or strict runoff guidelines. These contain plant-safe, low-toxicity formulas.

DIY Options (Vinegar, Baking Soda, Dish Soap | When They Work & When They Don’t)

DIY works only for:

Light dirt
Mild mildew
Small organic stains

Not suitable for heavy oil, deep grime, or rust.

What to Spray on Concrete Before Pressure Washing for Specific Problems

For Oil Stains

Use an alkaline degreaser with surfactants. Let it dwell 10–20 minutes.

For Rust Stains

Acidic rust removers work best. Avoid DIY methods rust bonds tightly to concrete.

For Tire Marks

Use solvent-based or alkaline cleaners designed to dissolve rubber residue.

For Mold, Mildew & Algae

Apply a mold/mildew remover with sodium hypochlorite. Let it sit until discoloration fades.

For Irrigation or Hard Water Stains

Use an acidic mineral remover.

For Food, Grease & Organic Spills

Enzymatic cleaners outperform typical detergents in these cases.

What to Spray on Concrete Before Pressure Washing for Old, Stubborn Stains

Old stains require:

High-strength degreasers
Acidic cleaners (for rust/irrigation marks)
Long dwell time
Agitation with a stiff brush

The Science Behind Concrete Pre-Treat Cleaners

Surfactants & How They Lift Stains

Surfactants lower surface tension, allowing the solution to penetrate pores and lift dirt from within.

pH Levels: Acidic vs Alkaline Cleaners

Alkaline (High pH): Remove grease, oils, organic stains
Acidic (Low pH): Remove minerals, rust, contaminants

Why Dwell Time Is Critical for Results

The cleaner must remain on the surface long enough to chemically break down what you intend to remove. Too little dwell time = weak results.

Step-by-Step Guide: What to Spray on Concrete Before Pressure Washing

Step 1 — Identify the Type of Stain

Evaluate whether you’re dealing with oil, mildew, rust, or general grime.

Step 2 — Choose the Correct Pre-Treatment Solution

Use:

Detergents for general dirt
Degreasers for oil
Mold removers for algae
Acidic cleaners for rust

Step 3 — Apply the Pre-Spray Evenly

Use a pump sprayer or downstream injector for larger surfaces.

Step 4 — Let the Cleaner Dwell

Typical dwell times:

Detergents: 5–10 minutes
Degreasers: 10–20 minutes
Mold removers: 10–15 minutes
Acidic cleaners: 5–10 minutes

Step 5 — Agitate (When Necessary)

Stubborn stains benefit from brushing to increase penetration.

Step 6 — Rinse or Pressure Wash Properly

Use appropriate PSI:

2,500–3,200 PSI for driveways
1,500–2,000 PSI for delicate concrete

Step 7 — Post-Wash Treatment

Optional steps:

Apply sealers
Repeat cleaning for heavy buildup
Apply a post-treatment to prevent regrowth

Comparison Table: What to Spray on Concrete Before Pressure Washing

Type of Pre-Spray	Best For	Strength	Cost	Safe for Plants?	Dwell Time	Pros	Cons
Concrete Detergent	General cleaning	Medium	Low	Yes	5–10 mins	Versatile	Not strong for oil
Degreaser	Oil/grease	High	Medium	Often No	10–20 mins	Powerful	Can harm grass
Mold/Mildew Remover	Organic growth	High	Medium	Sometimes	10–15 mins	Kills spores	Needs thorough rinsing
Enzymatic Cleaner	Organic stains	Medium	High	Yes	20–60 mins	Natural	Slow acting
Acidic Cleaner	Rust/mineral stains	Very High	Medium	No	5–10 mins	Instant results	Corrosive
DIY Mixes	Light dirt	Low	Very Low	Yes	10–20 mins	Affordable	Weak cleaning power

Safety & Environmental Guidelines

Plant & Landscaping Protection

Pre-wet plants and cover them when using harsh chemicals.

Chemical Handling and PPE

Wear gloves, goggles, and non-slip shoes. Follow all label instructions.

Avoiding Surface Damage

Do not use overly strong chemicals on stamped, sealed, or decorative concrete.

Local Runoff Regulations to Consider

Some cities require environmentally safe cleaners to avoid contaminating storm drains.

Professional vs DIY: Who Should Use Which Pre-Spray?

When DIY Pre-Spray Is Good Enough

For light dirt, mildew, or small stains, DIY methods and general detergents work fine.

When You Need Professional-Grade Detergents

Choose commercial products for:

Oil
Engine leaks
Rust
Deep organic stains

Cost Comparison: DIY vs Professional Cleaner

DIY: $5–$15
Professional-grade: $20–$50
Commercial contractor: $150–$400

Results Comparison

Professionals consistently achieve deeper, longer-lasting results due to specialized chemicals and equipment.

What to Spray on Concrete Before Pressure Washing (Full Expert List + Usage Guide)

The top recommended products include:

Concrete detergents
Alkaline degreasers
Mold/mildew removers
Enzymatic cleaners
Acidic rust removers
Eco-friendly green cleaners
DIY mixes for light dirt

FAQs

What is the best chemical to spray on concrete before pressure washing?

A degreaser for oil, an acidic cleaner for rust, and a detergent for general dirt.

Do you need a degreaser before pressure washing driveways?

If there are oil stains, absolutely pressure alone cannot remove petroleum.

What is the safest pre-treat for concrete around plants?

Biodegradable, plant-safe detergents or enzyme cleaners.

Can bleach be used as a pre-wash for concrete?

Yes, for mold/mildew but avoid using it regularly and never on sealed surfaces.

How long should pre-spray dwell before washing?

Typically 5–20 minutes depending on the product.

Will pre-treat solutions damage sealed or stamped concrete?

Some may. Always test a small area first.

What is the best pre-spray for old concrete stains?

A commercial-grade degreaser or acidic cleaner combined with agitation.

Do professionals always pre-treat concrete?

Yes pre-treatment is standard practice for achieving top-tier results.

Conclusion

Knowing what to spray on concrete before pressure washing is the key to restoring concrete quickly and effectively. Pre-treatments like detergents, degreasers, mold removers, and specialty cleaners make pressure washing significantly more efficient and ensure deeper, longer-lasting results. Match the product to the stain type, follow proper dwell times, and always prioritize safety and environmental care. For professional-grade results without the hassle, trust Stegmeier Pressure Washing
to handle all your concrete cleaning needs experienced, reliable, and guaranteed to leave your surfaces spotless.