A pressure washer soap dispenser typically works by using the Venturi effect, a principle of fluid dynamics where a reduction in fluid pressure occurs when a fluid flows through a constricted section (or choke) of a pipe. This pressure reduction allows soap to be drawn into the water stream.
Understanding the Mechanism: The Venturi Effect
At its core, the most common type of pressure washer soap dispenser, often called a downstream injector, relies on creating a lower-pressure zone within the high-pressure water flow.
Here's a breakdown of the process:
- High-Pressure Flow: Water from the pressure washer pump flows at high speed through a specially designed chamber or injector body.
- Constriction Point: Within this chamber, there is a narrowed section. As the water rushes through this constriction, its velocity increases, and according to the Venturi effect, the pressure drops significantly in this specific area.
- Creating a Vacuum/Low Pressure: The pressure in the constricted zone becomes lower than the atmospheric pressure of the surroundings.
- Drawing the Soap: This low-pressure zone creates a suction force. A little tube, connected to the injector and placed in your soap container (like a bucket or the pressure washer's soap tank), allows this suction to draw soap out of the container and into the water stream. This process is similar to how you might draw liquid through a straw.
- Mixing: The drawn soap then mixes with the high-pressure water flow before exiting the pressure washer hose, usually applied at a lower pressure setting suitable for cleaning.
Reference Insight: As mentioned in discussions about how these systems work, a key component is this little tube that facilitates the suction, allowing the system to draw soap out of your chosen container.
Components Involved
The typical downstream soap dispensing system involves a few key parts:
- Injector Body: The main housing where the Venturi effect is created.
- Soap Inlet Port: The connection point on the injector for the soap tube.
- Suction Tube: The little tube that goes from the injector into the soap container.
- Check Valve (often included): Prevents water from flowing back into the soap container.
- Orifice/Nozzle: The constriction point within the injector body that creates the pressure drop.
How Soap Application Changes
When using a soap dispenser (especially the downstream injector type), you typically need to switch to a low-pressure setting or use a specific soaping nozzle on your wand. High pressure (like that used for blasting dirt) prevents the injector from drawing soap effectively because the Venturi effect relies on a pressure differential that isn't significant enough at peak operating pressure.
Here's a simple comparison:
| Feature | High-Pressure Cleaning | Low-Pressure/Soap Application |
|---|---|---|
| Water Pressure | High | Low |
| Soap Dispensing | Inactive (Venturi effect negated) | Active (Venturi effect works) |
| Nozzle Type | Narrow (0°, 15°, 25°, etc.) | Wide Angle or Specialty Soap Nozzle |
By switching to a low-pressure nozzle (often a black tip), the water flow rate changes, allowing the injector to effectively create the vacuum needed to draw soap through the little tube.
In summary, a pressure washer soap dispenser utilizing the Venturi effect works by using the flow of high-pressure water through a restricted area to create suction, which pulls soap through a tube from a container into the water stream for application.
