Three Types of Injectors: Which One Should I Use?

September 9, 2021

As you plan your constant liquid feed fertilizer program, which injector to use is one of the most important decisions you’ll make. There are many methods for chemical injection into the water line and many injectors of various types on the market today. This article discusses the benefits and drawbacks of three of the major injectors you might choose.

Siphon Mixers (Venturi-Type Injectors)

Siphon Mixers, or Venturi-type injectors, use the pressure difference between the stock tank and water line to pull concentrated fertilizer solution through a flexible tube into the waterline. Since the method depends on water pressure, the injection rate can vary based on water flow. The injection ratio is low, around 1:16 or 1:20, and most Venturi-type injectors require at least 35 psi water pressure to work. These injectors need large stock tanks and work best for small areas.

Benefits

Siphon mixers are inexpensive. You can purchase one for under $20.
The Venturi-type injectors are easy to install. Simply insert the flexible tube into the stock tank and attach the valve to the faucet.

Drawbacks

Siphon Mixer injection rate changes based on water flow. The higher the water flow, the higher the injection rate. Since the ratio is variable, the Venturi-type injector requires extremely constant flow and pressure to be reliable.
Calculations for how strong to mix the concentrated fertilizer solution can be complicated. You’ll have to work backward from the nutrient solution uptake to know exactly how strong to mix concentrated fertilizer in the stock tank.
This injector won’t handle high water flow.

Small Scale Proportioning Injectors

Small scale proportioning injectors use positive displacement technology to inject a specific amount of liquid fertilizer concentrate into a specified amount of irrigation water, both of which are controlled by the unit. Most small scale proportioning injectors use water pressure rather than electricity for power.

Benefits

Accurate dosing is adjustable on the pump, which offers reliable injection ratios.
Small scale proportioning injectors range in cost from $100-$400 depending on the brand, ratio range, and features.
These injectors tend to have a decent lifespan.
The proportioning injector is easy to repair because it doesn’t have any electric components.

Drawbacks

Proportioning injectors are more complicated to install than Venturi-type injectors. The inlet/outlet section of the injector must be installed to line up with the main water pipe in the proper direction.
Small scale proportioning injectors can’t handle high water flow. Whereas Commercial Proportioning Injectors handle up to 40 Gallons Per Minute (GPM), small scale injectors only go to 11 GPM.

Commercial Proportioning Injectors

Commercial proportioning injectors use the same technology as small scale proportioning injectors but have a much higher capacity for high water flow and a wider range of operating pressures and injection capabilities.

Benefits

Commercial proportioning injectors dose accurately and are adjustable.
They last longer than small scale proportioning injectors or siphon mixers.
Commercial injectors can handle water flow up to 40 GPM.

Drawbacks

Commercial proportioning injectors can be more difficult to repair.
They are more expensive, ranging from $900-$1,400.

Considerations

As you research and choose an injector for your constant liquid feed fertilizer program, consider:

The size of your grow
The amount of money you want to invest in your fertilizer system
How constant the flow and pressure of your water system is and how reliably accurate the fertilizer system needs to be

For more information about various types of fertilizer injectors, look here and here.