Using a Downstream Injector

Understanding Downstream Injectors:

Downstream injectors operate by drawing cleaning solutions or detergents into the water stream after it passes through the pump. This ensures that the cleaning agent is introduced only when needed, preventing any potential damage to the pressure washer's pump or components. The process is straightforward, offering a practical and efficient way to clean houses, trucks, cars, etc.

Differential Pressure: Downstream injectors take advantage of the difference in pressure between the high-pressure water flow from the pressure washer pump and the lower pressure created in the injector. The pressure drop in the injector creates a suction effect, allowing it to draw in and mix chemicals without the need for an additional pump. This is a result of the venturi effect.

Venturi Effect: Central to the operation of downstream injectors is the Venturi effect, a fluid dynamics principle describing the reduction in pressure that occurs when a fluid flows through a constricted section of a pipe. In the case of downstream injectors, the narrowing of the flow path within the injector creates a Venturi effect. This pressure drop in the constriction facilitates the suction of chemicals or additives into the water stream.

Now, let's delve into the practical steps on how to use downstream injectors effectively with pressure washers:

  1. Selecting the Right Downstream Injector: Begin by choosing a downstream injector that is compatible with your pressure washer. Consider factors such as flow rate (GPM), pressure rating, and chemical compatibility. All of the injectors that TWRP carries are compatible with most pressure washers and our staff are happy to help you select the correct size.

  2. Installing the Downstream Injector: Position the downstream injector after the pressure washer pump, usually connected to the hose reel swivel. We recommend having a male and female quick-connect fitting for quick and easy installation and removal. Securely attach the injector, ensuring proper alignment with the water flow (there is an arow showing the flow direction on each injector).

  3. Adjusting Injector Settings: If you purchased an adjustable injector, consult the manufacturer's instructions to set these parameters according to the concentration recommended for your specific cleaning agent. All of the chemicals TWRP sells will have recommended ratios provided.

  4. Start the Pressure Washer: With the downstream injector installed and with the hose in a tank or bucket of fresh water, start the pressure washer. Allow your washer to run and warm up.

  5. Engaging the Downstream Injector: Once the pressure washer is fully running and while off of the trigger, drop the injector line into your cleaning solution. Put the appropriate soap nozzle on your gun and pull the trigger in an out of the way area until you see soap coming from your gun.

  6. Cleaning Operation: Proceed with your cleaning procedure, applying from the bottom up. The downstream injector will automatically introduce the cleaning agent into the water stream so long as you are using the correct soap nozzles.

  7. Rinsing: To disengage the injector, put the appropriate rinse nozzle on your gun. Always rinse from the top down. Note that if you have a downstream injector installed, flow will be reduced slightly. This will not be an issue in most cases. However, if you are performing cleaning procedures with other attachments like a surface cleaner, you will not get the right flow or pressure for optimal performance. 
  8. Adjusting Dilution Ratio (If Necessary): Throughout the cleaning process, monitor the dilution ratio of the cleaning agent. Adjustable downstream injectors allow for on-the-fly adjustments. If needed, fine-tune the dilution ratio to meet the specific cleaning requirements. When using a fixed flow injector, add water to your solution to lower the concentration. Add chemical to increase the concentration. Keep in mind that downstream injectors can only get up to a certain mix ratio (normally the highest being 1:5). For more concentrated application, you will need a different system such as a 12 volt or gas soft wash system or an X-Jet.

  9. Shutting Down the System: When the cleaning task is complete, always make sure to take the injector hose out of the chemical solution and put it into a supply of fresh water. Rinse the injector by opening your ball valve all the way or pulling the trigger with a soap nozzle on. Rinse for at least two minutes. If you do not rinse your injector, premature failure and clogging WILL happen. Always rinse.

  10. Storage: After use, remove your injector from the hose line. Keeping it connected when not in use may cause premature failure. We advise spraying some penetrating oil into the quick connects and injector periodically to keep it from corroding and breaking.

Down streaming is an excellent way of cleaning a variety of surfaces but does have its limitations. For applications where higher concentrations are required such as roofs and porous surfaces, a soft wash system or X-Jet will be necessary.

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