The Short Answer
Match the pressure washer detergent to the surface: degreaser for concrete and oil-stained flatwork, general detergent for the daily exterior route, and soft wash chemistry built around sodium hypochlorite for siding and roofs, applied through the machine's downstream or upstream injector. The soap does the dissolving, and the pressure carries it. Detergent is the solvent, and pressure is the delivery system.
The seal rule comes first. The machine's hoses, seals, and fittings are the parts that detergents can damage, and the harsh concentrates, applied wrong or left sitting, are the ones that do it. The commercial route reads the chemical label the way it reads the surface, because the pump outlives the job. The machine is only as safe as the chemistry it is fed.
Detergent Chemistry: Downstream, Upstream, and the Surface
Downstream injection adds the detergent after the water leaves the pump, which keeps the concentrate out of the pump's internals, and upstream injection draws the chemical into the water before the pump, which puts the concentrate through the machine. The two delivery styles shape which chemicals a rig can safely run and how the soap ratio behaves at the wand. The injector style is the machine's chemistry policy. Know which side of the pump the soap enters, because the seals do.
Degreaser is the detergent lane for concrete: the oil, grease, and tire-mark buildup that pressure alone redistributes instead of removes. The degreaser dissolves the petroleum load, and the pressure and rinse carry it off the flatwork. The commercial concrete route runs on the degreaser pass, which is why the machine's detergent tanks and injectors earn their keep on those jobs. Degreaser is the chemistry that makes the concrete bid honest. Pressure moves the dirt that chemistry has already loosened.
General detergent, the neutral soap lane, covers the daily exterior route: siding, storefronts, walkways, and the washdowns where the load is dust and grime instead of grease. The formula is built to clean without etching the surface or attacking the machine, which makes it the safe default between the specialty passes. The general detergent is the route's everyday chemistry. Most of the week is a neutral-soap week.
The soft wash lane runs on chemistry instead of pressure: formulas built around SH, shorthand for sodium hypochlorite, applied at low pressure to siding, roofs, and the surfaces where the stream would do the damage. The chemistry kills the organic load, the mold, algae, and mildew, and the low-pressure rinse carries it off. Soft wash chemistry is the answer when pressure is the wrong tool. Sometimes the chemical should do the work, and the machine should just deliver it.
The pressure washer is the delivery truck, and the detergent is the cargo: degreaser for the concrete loads, general detergent for the daily route, and soft wash chemistry for the delicate stops. The truck runs best on the cargo it was built to carry. Match the chemical to the surface, and the machine lasts the route. Every surface has its chemistry, and the seals have their limits.
| Surface | Chemistry lane | Why |
|---|---|---|
| Concrete with oil and grease | Degreaser | Dissolves the petroleum load pressure cannot move |
| Siding and storefronts | General detergent | Neutral cleaning without etching the surface |
| Roofs and delicate siding | Soft wash with SH | Chemistry kills the organic load at low pressure |
| Daily mixed exterior route | General detergent | The safe default between specialty passes |
What This Means for Your Operation
Stock the truck by the route. Degreaser for the concrete bids, general detergent for the daily washdowns, and soft wash chemistry for the delicate surfaces, delivered through the machine's injector system. The soft wash vs pressure wash comparison covers when the chemistry should replace the pressure entirely.
Frequently Asked Questions
What detergent should I use in a commercial pressure washer?
What is the difference between downstream and upstream injection?
What pressure washer detergent eats seals?
Is sodium hypochlorite used in pressure washing?
Reference Standards for This Category
Published standards and programs that buyers in this category are typically accountable to. Listed for context, not as an endorsement of any product on this page.
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