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Downstream Injector with Pressure Washer Overview

Downstream Injecting with Pressure Washers

Downstream injecting is an effective method for mixing chemicals with water after the pump in a pressure washer system. This technique is advantageous as it prevents bleach or other caustic substances from running through the pump head, thereby protecting the pump from potential damage. The downstream injector operates by drawing chemicals into the pressure washer hose under low line pressure and spraying the cleaning chemical mix out through a low-pressure nozzle. It is installed after the pressure washer pump head.

However, downstream injectors may not always perform optimally in all situations. To maximize the efficiency and effectiveness of a downstream injector, several key factors need to be considered:

1. Gravity

One significant factor influencing the performance of a downstream injector is gravity. When spraying at heights, the injector can stop working because the low-pressure nozzle gains elevation relative to the injector, increasing the back pressure. This back pressure can eventually reach a point where the downstream injector can no longer draw chemicals. Typically, this issue arises at heights of 15 to 20 feet, though it can occur at shorter distances depending on the length of the pressure hose used.

2. Hose Length

The length of the pressure hose also plays a crucial role in the functionality of downstream injectors. Generally, these injectors are effective with up to about 200 feet of pressure hose. Beyond this length, they may stop drawing chemicals due to increased resistance and reduced efficiency in the chemical draw process.

3. Injector Size

Selecting the correct size of the injector for your pressure washer is essential for proper operation. The size of the injector must match the flow rate (GPM - gallons per minute) of your pressure washer:

  • Size 1.8 injectors are suitable for 2-3 GPM machines.
  • Size 2.1 injectors work well with 3-5 GPM machines.
  • Size 2.3 injectors are designed for 6-8 GPM machines.

Using an injector that is too small for the pressure washer will result in inadequate chemical draw, compromising the cleaning process.

4. Nozzle Size

The size of the nozzle used in conjunction with the downstream injector is another critical factor. 

For machines with a flow rate of 3-5 GPM, a nozzle with an orifice size of at least 30-40 is necessary to ensure proper chemical draw. 

For 8 GPM machines, a nozzle with an orifice size of 50-60 is required. 

If the nozzle size is too small, it creates excessive pressure, preventing the Venturi effect, which is essential for the suction process to occur. A simple test to check for proper chemical draw is to operate the pressure washer without a nozzle and observe if there is a flow of soap.

Conclusion

Downstream injecting is a beneficial technique for mixing chemicals in pressure washer systems, avoiding direct chemical exposure to the pump head. To achieve the best results, it is important to consider factors such as gravity, hose length, injector size, and nozzle size. Properly addressing these factors will ensure efficient and effective use of downstream injectors, leading to optimal cleaning performance.