So, what kind of soap to use in a pressure washer? It's actually a bit of science. Just like you select a specific cleaner for your dishes or laundry, there's a soap that's just right for every job your pressure washer might tackle. Let's take a look at the types of soaps and the 3 best pressure washer soaps available today.
Quick Verdict: What Kind of Soap Should You Use?
- Always Use Pressure-Rated Detergents: Never run regular dish soap (like Dawn) through your machine—it contains salt, leaves sticky pump deposits, and strips wax.
- Match Chemical to Soil: Use pH-neutral snow foam for vehicles, peroxide/all-purpose cleaners for siding, alkaline degreasers for grease/driveways, and sodium hypochlorite (SH) for mold and black algae.
- Venturi Siphon Requires Black Nozzle: Downstream injectors only draw soap when backpressure stays below 250 PSI; you must insert the wide 65° black soap nozzle.
Venturi Siphon Pressure Differential (Bernoulli Principle)
Downstream detergent injectors rely on fluid velocity acceleration through an internal throat restriction to generate a low-pressure vacuum zone that draws chemical into the water stream.
Engineering Insight: Siphon vacuum occurs only when downstream line backpressure remains below 250 PSI. High-pressure tips (0° to 40°) build backpressure that kills the suction vacuum; only wide black soap tips allow chemical draw.
OPEN CHEMICAL DILUTION CALCULATORTypes of Soap for Pressure Washers
Let's make it simple. The soap you pick should match what you're cleaning. Here are the main types you'll see on the shelf:
| Soap Type | Recommended Option | pH Profile | Best Used On | Application Method | Amazon Link |
|---|---|---|---|---|---|
| All-Purpose Cleaner | Simple Green Oxy Solve | pH Neutral (~7.0) | Vinyl siding, composite decks, outdoor furniture | Downstream siphon tube (black nozzle) | Check Amazon |
| Auto Snow Foam | Chemical Guys Honeydew | pH Neutral (7.0) | Cars, trucks, RVs, motorbikes, clear coats | Dedicated foam cannon (1:5 dilution) | Check Amazon |
| Heavy Degreaser | Sun Joe SPX-APC1G | Alkaline (~9.5) | Concrete driveways, garage floors, BBQ grills | On-board soap tank or pump sprayer | Check Amazon |
| Sodium Hypochlorite | Contractor Grade SH | Strong Alkaline (11-13) | Heavy mold, black algae, roof gloeocapsa | Soft-wash proportioner or X-Jet M-Jet | Read SH Guide → |
Can You Use Dish Soap (Like Dawn) in a Pressure Washer?
It is strongly not recommended. Household dish soaps contain high salt concentrations (sodium chloride) and thick foaming surfactants that leave gummy residues in internal injector valves and dry out rubber seals. On top of that, dish soap strips automotive clear coat wax. For severe organic stains like mold and black algae, standard soaps are replaced by sodium hypochlorite—learn how soft-wash contractors mix bleach safely in our guide on what is SH in pressure washing.
Best Pressure Washer Soaps
Best for Overall Use - Simple Green Oxy Solve All-Purpose Pressure Washer Cleaner
The Simple Green Oxy Solve Total Outdoor Pressure Washer Cleaner offers powerful, eco-friendly outdoor cleaning.
Key Features:
- Versatile: Can clean a vast range of surfaces.
- Effective: Lifts dirt, grime, and stains caused by mold, mildew, moss, and algae.
- Safe: Uses the power of peroxide, it's eco-friendly and biodegradable, adhering to the U.S. EPA's Safer Choice program criteria.
- Peroxide Power: Uses fast-acting hydrogen peroxide to lift tough organic stains and dirt without chlorine odor.
- Surface Safe: Safe for vinyl, wood, composite decking, stucco, painted brick, and wicker patio furniture.
- EPA Safer Choice: Biodegradable, non-toxic formula that won't harm landscaping plants, pets, or lawn grass.
- Concentrated: 1 gallon of concentrate makes up to 21 gallons of washing solution.
Best Pressure Washing Soap for Cars - Chemical Guys CWS 110 Honeydew
The Chemical Guys Honeydew Snow Foam Car Wash Soap and Cleanser is an excellent choice for vehicle owners who prioritize both effectiveness and safety in their car care regimen.
Key Features:
- Surface Decontamination: The soap is engineered to lift road film, dirt, and atmospheric fallout with high lubricity, while protecting sensitive clear coats.
- Safe formula: The pH-neutral formula means it won't strip wax or sealants, so it's safe for regular use. Plus, it's detergent-free and won't scratch or leave water spots.
- Snow Foam: Ideal for foam cannons and foam guns for a super quick car cleaning experience.
- Ultra-Thick Foam Blanket: Traps dirt particles and lifts abrasive road grime away from delicate paint surfaces.
- 100% pH Neutral: Safely cleans without stripping protective carnauba wax, sealant, or ceramic coatings.
- High Lubricity: Eliminates wash-induced swirl marks and light micro-scratches during contact washing.
- Foam Cannon Optimized: Formulated to produce rich, clinging suds with residential electric and gas washers.
Best for Heavy-Duty Cleaning - Sun Joe SPX-APC1G Cleaner + Degreaser
The Sun Joe SPX-APC1G is an excellent cleaning solution that can handle heavy-duty tasks with ease.
Key Features:
- Versatile Cleaner: This all-purpose cleaner is versatile and highly effective, ideal for a variety of outdoor cleaning tasks—from decking and fencing to sidewalk and patio furniture, and even cars, RVs, boats, and more.
- Heavy Duty: Its strong formulation makes it a great degreaser, perfect for grills, outdoor equipment, and heavily soiled areas.
- Concentration: The 1-gallon concentrate can make up to 20 gallons of cleaning solution, providing excellent coverage for large cleaning tasks.
- Powerful Grease Cutting: Alkaline formulation emulsifies tough motor oil, tire rubber, and BBQ grease stains.
- High Concentration: 1 gallon of concentrate makes up to 20 gallons of cleaning solution for large exterior projects.
- Versatile Application: Excellent for concrete driveways, garage slabs, lawn equipment, boats, and vinyl siding.
- Biodegradable: Eco-friendly formulation safe for surrounding garden soil when rinsed properly.
Soap Application Tips
- Start Dry – Apply soap before wetting the surface.
- Keep It Wet – Don’t let soap dry; work in sections.
- Adjust Pressure – Match pressure to the surface.
- Bottom Up, Top Down – Soap from bottom, rinse from top.
- Overlap Sprays – Avoid missed spots with overlapping passes.
- Go Slow – Let soap sit and do the work.
- Rinse the Machine – Flush with clean water after use.
- Stay Safe – Wear gloves and goggles.
