Quick verdict
The Karcher Multi-Purpose Detergent is the best all-round pick. It is a highly concentrated formula that makes up to 40 gallons of cleaner from a single gallon, works with most consumer gas and electric washers or a foam cannon, and handles concrete, siding, driveways, cars, and more. That versatility and dilution ratio make it the easiest general-purpose starting point.
Karcher Multi-Purpose Pressure Washer Detergent
The Karcher is a highly concentrated multi-purpose detergent that makes up to 40 gallons of cleaner from a single gallon, so a little goes a long way. It is formulated to work with most consumer gas and electric pressure washers, or through a foam cannon, and it targets dirt and grime on concrete, pavement, driveways, patios, decks, RVs, cars, boats, and fencing. Made in the USA, it is the versatile pick for general exterior cleaning.
The best pressure washer soap picks compared by dilution, surfaces, and formula, from concentrated multi-purpose detergent to peroxide cleaners for mold and
Why you should trust this guide
Pressure washer soap is easy to overlook, but the right formula makes the difference between a quick clean and repeated passes on a stubborn stain. I built this guide by reading each product’s published description and comparing what actually matters: whether it is a concentrate, which surfaces it targets, the type of grime it addresses, and how it dilutes. Because these listings vary in detail, I separated the general-purpose detergents from the specialized peroxide stain cleaners.
My goal is to help you match the soap to your job rather than guess. I note which products are broad multi-purpose cleaners, which are focused on siding, and which use a peroxide formula aimed at algae, moss, and mildew. Where a listing is sparse and does not state clear dilution or coverage, I say so plainly instead of filling in numbers that are not there.
How we evaluated
I evaluated these soaps on the criteria that decide real cleaning results: whether they are concentrated and how far they dilute, the surfaces they are formulated for, the type of grime they target, and pressure-washer and foam-cannon compatibility. Because the right chemistry depends on the stain, I weighted surface suitability and grime type heavily, distinguishing general dirt from organic algae and mildew staining.
I did not test these products, so nothing here reflects a physical trial. I compared the documented descriptions and any stated coverage or dilution, and where a listing did not provide those figures I noted the gap rather than inventing values. I grouped the picks by purpose, so a general-purpose detergent and a peroxide stain cleaner are compared for what each is genuinely built to do.
What to look for
- Concentrate versus ready-to-use: a concentrate that dilutes far, like one gallon making 40, stretches further and costs less per job.
- Target surfaces: check the label lists your materials, whether concrete, vinyl siding, wood, brick, or stucco.
- Grime type: general detergents handle everyday dirt, while peroxide formulas target algae, moss, and mildew stains.
- Formula safety: peroxide and Safer Choice certified cleaners are gentler options around plants, pets, and children.
- Application method: confirm it works with your pressure washer’s soap system or a foam cannon, not just manual use.
- Coverage: where stated, coverage per bottle helps compare value, though it varies with dilution and stain severity.
- Surface compatibility: match the cleaner to delicate surfaces carefully, since a strong formula can affect finishes.
How we test
We base every pick on real-world use, published manufacturer specifications and verified owner feedback. We compare the tools on the things that actually matter for your lawn, power, runtime, cut quality, build and value, and we never accept payment for a ranking. When we have not used a specific model first-hand, we say so.
The picks at a glance
| Tool | Best for | Score | |
|---|---|---|---|
| Karcher Multi-Purpose Pressure Washer Detergent | Best Overall | Check price | |
| Zep House and Siding Wash (128 oz) | Best Value | Check price | |
| Zep All-in-1 Pressure Washing Concentrate (172 oz) | Best Premium | Check price | |
| Oxy Solve House and Siding Cleaner | Best Budget | Check price | |
| Simple Green Oxy Solve Total Outdoor Cleaner | Also Great | Check price |
The picks, reviewed
Karcher Multi-Purpose Pressure Washer Detergent
The Karcher is a highly concentrated multi-purpose detergent that makes up to 40 gallons of cleaner from a single gallon, so a little goes a long way. It is formulated to work with most consumer gas and electric pressure washers, or through a foam cannon, and it targets dirt and grime on concrete, pavement, driveways, patios, decks, RVs, cars, boats, and fencing. Made in the USA, it is the versatile pick for general exterior cleaning.
Reasons to avoid
- As a general-purpose cleaner it is less specialized for heavy algae or mold than the peroxide formulas here
- You must follow the label dilution to avoid wasting concentrate or over-applying
Zep House and Siding Wash (128 oz)
This Zep house and siding wash is a concentrate that the listing says covers up to 5,000 square feet and makes up to 20 gallons of cleaner, aimed specifically at siding. It is a straightforward value pick for washing down the exterior of a house before or between deeper cleanings. The focused formula keeps it simple for its intended siding job.
Reasons to avoid
- The listing is sparse, so it lists fewer surface details than the multi-purpose options
- It is oriented toward siding rather than a broad range of surfaces
Zep All-in-1 Pressure Washing Concentrate (172 oz)
The Zep all-in-1 is a larger 172-ounce pressure washing concentrate marketed as an all-in-one cleaner for siding, driveways, brick, wood, and stucco, and it targets stains caused by algae. The bigger bottle suits larger or more frequent jobs across mixed exterior materials. It is the pick for buyers who want one concentrate that spans several common surfaces.
Reasons to avoid
- Its product details are limited, so exact dilution and coverage are not clearly stated
- It focuses on general cleaning and algae rather than heavy mold or mildew remediation
Oxy Solve House and Siding Cleaner
The Oxy Solve is a one-gallon concentrate that uses the power of peroxide to lift grime without harsh chemicals, targeting stains and discoloring from algae, moss, and mildew on vinyl, aluminum, stucco, wood, and brick. It is described as a safer, orally non-toxic formula and cleans up to 6,400 square feet per bottle. That combination of gentler chemistry and stain focus makes it the value pick for organic staining.
Reasons to avoid
- A peroxide cleaner is aimed at algae and mildew stains, not heavy grease or oil
- Coverage depends on dilution and how heavily stained the surface is
Simple Green Oxy Solve Total Outdoor Cleaner
The Simple Green Oxy Solve is a peroxide-powered concentrate that is EPA Safer Choice certified and cleans decks, siding, driveways, and patios on wood, vinyl, concrete, brick, and composite. It covers up to 6,400 square feet per bottle and works with a pressure washer or by manual application, with a formula the listing describes as gentler around children and pets. It is a strong alternative for eco-minded users tackling organic grime.
Reasons to avoid
- Like the other peroxide cleaner it is best for algae and mildew rather than grease
- Real coverage varies with dilution and stain severity
What to look for
Concentrate and dilution
A concentrate that dilutes far stretches your money, and the Karcher making up to 40 gallons from one is a good example. Always follow the label ratio, since over-concentrating wastes product and can be harsher on surfaces than needed.
Match the soap to the grime
General-purpose detergents handle everyday dirt and light grime across many surfaces, while peroxide-based cleaners are built specifically for algae, moss, and mildew stains. Identify whether your problem is general dirt or organic staining before choosing.
Surface compatibility
Check that the label lists the materials you are cleaning, whether concrete, vinyl or aluminum siding, wood, brick, or stucco. Some formulas are broad while others are focused on siding, and matching the cleaner to the surface protects finishes.
Formula safety
If you are cleaning near gardens, pets, or children, a peroxide-based or Safer Choice certified formula is a gentler option than a harsh chemical cleaner. These lift organic stains while being described as safer around living things, which matters for exterior home use.
Application method
Confirm the soap is compatible with your pressure washer's detergent injection or with a foam cannon, not just manual application. The listings note pressure-washer and foam-cannon use, which lets you apply and dwell the cleaner efficiently before rinsing.
Our verdict
The Karcher Multi-Purpose Detergent is the best all-round pick. It is a highly concentrated formula that makes up to 40 gallons of cleaner from a single gallon, works with most consumer gas and electric washers or a foam cannon, and handles concrete, siding, driveways, cars, and more. That versatility and dilution ratio make it the easiest general-purpose starting point.
FAQs
It is better to use a detergent formulated for pressure washers. These are designed to work with the machine's soap system or a foam cannon, dilute correctly, and rinse cleanly without harming surfaces or the pump.
A general-purpose detergent handles everyday dirt and light grime across many surfaces, while a peroxide cleaner like Oxy Solve or Simple Green targets algae, moss, and mildew stains with a gentler formula.
It depends on the product. The Karcher concentrate makes up to 40 gallons of cleaner from one gallon, and some peroxide cleaners state coverage up to 6,400 square feet per bottle. Always follow the label dilution for best results.
The peroxide-based options, including the Safer Choice certified Simple Green, are described as gentler around children, pets, and plants. Still, rinse nearby vegetation and follow the label directions for any formula.
Both the Zep house-and-siding washes and the peroxide cleaners list vinyl siding among their surfaces. For algae or mildew staining specifically, a peroxide formula is well suited, while a general wash handles routine dirt.