What is a Venturi System?
A venturi chemical injector or jet pump has a high pressure zone before the primary orifice and a low pressure zone after the orifice. The increased fluid velocity entering the low pressure zone creates a small vacuum, allowing a chemical to be drawn into the flow.
In other words, venturis work on the principle of differential pressure.
The pressure difference creates a vacuum at the suction port on the side of the device. So, the greater the difference in pressure, the greater the vacuum and, with that, the greater the volume of the chemical that it is able to suck up.
Venturis come in a number of different sizes. Size is determined not by the size of the pipeline into which it is installed, but rather by the pressure and flow rate of the water. Because of this, it is important to size the primary orifice to match the pump flow and pressure and the size of the final gun nozzle, which should be very much larger to allow the secondary pressure zone to be a lot lower than the primary one.
Hawk venturis come with an adjustable chemical needle valve, which cannot be calibrated, for where accuracy is not required. A fitting with a range of fixed metering orifices is available for accurate, non-variable addition of chemical.