Pressure washer soap and degreaser do different jobs. Soap, or general detergent, lifts dirt, dust, mud and road film; degreaser is built to break down oil, grease and carbon. Pick the chemistry by the soil you are removing, apply it at low pressure, let it dwell without drying, then rinse at full pressure. Water alone moves dirt around. Chemistry is what lets pressure finish the job in one pass.
This guide covers commercial use: fleet and equipment washing, dumpster pads, loading docks, drive-thrus and shop floors. It explains how soap injectors actually dose chemistry, how to mix concentrate so it lands at label strength, and what must never go through the pump.
- Soap lifts general dirt; degreaser breaks down oil and grease. Match the chemistry to the soil, not to the machine, or you will wash every surface twice.
- Chemistry goes on at low pressure and comes off at high pressure: apply with the black soap tip or a pump sprayer, let it dwell, then rinse with a 15° or 25° tip.
- Downstream injectors dilute a second time, commonly around 10 parts water to 1 part chemical, so pre-dilute concentrate in the siphon jug instead of pouring it in neat.
- Never pull bleach, acids or quaternary ammonium (quat) chemicals through a pressure washer pump. They attack seals, valves and the unloader; that is the costliest mistake made with these machines.
What Is the Difference Between Pressure Washer Soap and Degreaser?
Soap is a general-purpose detergent that loosens everyday dirt so water can carry it away; degreaser is formulated to break the bond between oil or grease and the surface. Using soap on grease just smears it, and using a heavy degreaser on light dirt wastes product.
| Soil | Chemistry | Typical jobs |
|---|---|---|
| Dust, mud, pollen, road film | Soap or all-purpose cleaner | Siding, sidewalks, trailers, general wash-down |
| Oil, grease, carbon | Degreaser | Engine bays, heavy equipment, dumpster pads, shop and dock concrete |
| Mixed heavy soil | Degreaser plus hot water | Fleet yards, truck shops, restaurant back lots |
How Do You Use Soap or Degreaser With a Pressure Washer?
Rinse off loose debris, apply the chemistry at low pressure, let it dwell, then rinse at high pressure. Work in sections small enough that the chemistry never dries before you rinse it.
- Clear loose debris. Sweep or give a quick rinse so the chemistry works on the bonded soil, not on loose grit.
- Mix to label strength. JANITORI Degreaser MAX No.72 runs at 20 mL per 4 L of water (1:200) for routine grease and 40 mL per 4 L for extreme buildup. If you feed it through an injector, use the siphon-jug chart below.
- Apply at low pressure. Use the black soap tip with the injector or a pump sprayer. On walls and vehicles, apply from the bottom up so runs do not streak the dry surface below.
- Let it dwell, but never dry. Give it a few minutes; in sun or wind work smaller sections and re-mist if needed.
- Agitate heavy soil. A brush on equipment, or a surface cleaner on flatwork, loosens what chemistry alone will not.
- Rinse at full pressure. Switch to a 15° or 25° tip and rinse from the top down, keeping runoff out of storm drains.
The pressure washer degreaser. Its label says it is ready to spray, mop or apply by pressure washer once mixed, it rinses residue-free with hot or cold water, and it contains no phosphates, petroleum solvents or VOCs. One 3.6 L jug makes about 720 L of working solution at 1:200.
For spot pre-treatment before the wash: spray straight onto a greasy fitting, hitch or drip mark, give it 30 to 60 seconds, and let the pressure washer rinse it off.
The soap side of the job, for dust, mud and road film rather than grease. Mix 5 mL per 2 L of water, pump-spray it onto concrete, plastic, stone or vehicle surfaces, let it work briefly, then rinse with the pressure washer.
How Does a Pressure Washer Soap Injector Work?
A downstream injector sits after the pump and uses a venturi to pull chemical into the water stream, but only when pressure at the wand is low. That is why chemistry only flows with the wide black soap tip installed, and stops as soon as you switch to a high-pressure tip.
- Downstream injection keeps chemical out of the pump entirely. It is the safe default and the only acceptable route for aggressive chemistry. The trade-off is low-pressure application and a second dilution.
- Upstream injection meters chemical in before the pump and is common on hot-water machines. Chemical passes through the pump, so only use products the pump maker allows.
- Pre-spraying with a pump-up sprayer applies chemistry at exact strength with no machine dilution at all. It is the best choice for spot work and heavy-duty mixes.
Most downstream injectors draw somewhere around 7 to 10 parts water per part chemical, and the real number changes with injector orifice, hose length and soap-tip size. Measure yours: put the soap line in a measuring jug of plain water, run the black tip for exactly one minute, and compare what it drew with your machine's gallons per minute. Every model in our commercial pressure washer range lists its GPM.
How Much Degreaser Goes in the Siphon Jug?
Enough that the injector's second dilution lands you at label strength. Pouring concentrate in neat wastes product; pouring in a bucket already mixed to 1:200 ends up roughly ten times too weak at the surface.
| Measured injector draw | Jug mix for routine grease (lands near 1:200) | Jug mix for heavy buildup (lands near 1:100) |
|---|---|---|
| 7:1 | 1 part No.72 to 24 parts water | 1 part No.72 to 12 parts water |
| 10:1 | 1 part No.72 to 17 parts water | 1 part No.72 to 8 parts water |
| 15:1 | 1 part No.72 to 12 parts water | 1 part No.72 to 5 parts water |
Upstream proportioners have their own metering valve, so set them per the machine manual instead of this chart.
Do You Need Hot Water to Degrease With a Pressure Washer?
Not for light or fresh grease, but hot water is the biggest upgrade for heavy, recurring grease. Heat thins oil and speeds up the degreaser, so the same job takes fewer passes and less product.
Hot-water machines such as the Pressure-Pro Hot Shot 4012-10C (4,000 PSI, 4.0 GPM) and the skid-mounted Pressure-Pro Pro Super Skid 6012PRO-10G (4,000 PSI, 5.5 GPM) are the standard in truck shops. For cold-water fleets, the Pressure-Pro Eagle II EB4040HC (4,000 PSI, 4.0 GPM, belt drive) pairs with longer dwell times to make up for the missing heat. For stubborn oil on concrete specifically, see how to get oil stains out of concrete.
What Should Never Go Through a Pressure Washer Pump?
Bleach, acids and quaternary ammonium (quat) chemicals. All three attack pump seals, valves and the unloader, and a failed pump costs far more than the chemistry you saved time with.
- Apply those products only through a downstream injector or a separate soft-wash system.
- Flush the injector and soap line with clean water at the end of the day so residue does not crystallize in the check valve.
- Do not use dish soap or household cleaners as a substitute. They are not formulated for injector systems and can foam heavily.
Where Does Pressure Washer Runoff Go?
Keep it out of storm drains. The EPA's stormwater guidance points out that storm drains lead directly to local waterways, not to treatment plants, and recommends biodegradable, phosphate-free, water-based detergents used in limited amounts (EPA stormwater BMP). Commercial wash sites fall under local rules and the EPA NPDES stormwater program, so check where your wash water is allowed to go before you start.
Dosing to the label is part of compliance, not just cost control: the less excess chemistry you put down, the less ends up in the runoff.
Frequently Asked Questions
Can you use dish soap in a pressure washer?
It is not recommended. Dish soap is formulated for hand washing, not for injector systems, and can foam heavily in the line. Use a product whose label allows pressure washer application, and pick degreaser for oil and grease.
Can you put degreaser in a pressure washer soap tank?
Yes, if the product's label allows pressure washer application and your machine's manufacturer allows it in the injector. JANITORI Degreaser MAX No.72 is labeled for pressure washer application; pre-dilute it in the siphon jug to account for the injector's draw.
Why is my pressure washer not pulling soap?
The most common cause is a high-pressure tip still installed; a downstream injector only draws with the wide black soap tip. Other causes are an injector sized for a different GPM, a very long hose, or a clogged strainer on the soap line.
How long should pressure washer soap sit before rinsing?
A few minutes, typically 5 to 10 for heavy soil, but never long enough to dry. In direct sun or wind, work smaller sections and re-mist so the chemistry stays wet until you rinse.
Is degreaser better than soap for concrete?
For oil, grease and tire marks, yes. For dust and general dirt, soap or an all-purpose cleaner is enough. Most commercial concrete jobs are oil-driven, which is why degreaser plus hot water is the standard for docks, shops and drive-thrus.
Related Guides
- What Is a Good Pressure Washer PSI? A Commercial Job Chart With GPM
- Pressure Washer Nozzle Chart: Colors, Angles and Tip Sizes
- How to Get Oil Stains Out of Concrete
- How to Clean a Concrete Floor