Mazzei Air Injectors (selection and installation)

Mazzei Injectors
Mazzei® Injectors are high-efficiency, Venturi-type, differential pressure injectors with internal mixing
vanes. When a sufficient pressure difference exists between the inlet and outlet sides of the injector, a
vacuum is created inside the injector body, which initiates suction of a liquid or gas through the
suction port.
How a Mazzei® Injector Works
When pressurized water enters the injector inlet, it is constricted toward the injection chamber and
changes into a high-velocity jet stream. The increase in velocity through the injection chamber results
in a decrease in absolute pressure, creating a vacuum, thereby enabling an additive material to be
drawn through the suction port and entrained into the water stream. As the jet stream is diffused
toward the injector outlet, its velocity is reduced and it is reconverted into lower pressure energy.
TYPICAL INSTALLATIONS
Performance
Mazzei Injectors operate over a wide range of pressures and require only a minimal pressure
differential between the inlet and outlet sides to initiate a vacuum at the suction port. Click here to
view Injector performance tables in US and metric. The performance tables are divided in two
sections: liquid suction and gas suction.
Why Mazzei
• Proven performance with years of expected service
• No electrical connections needed
• Can run dry with no problems
• Considerable cost savings versus other injection methods
• Safe to use as the chemicals are injected under vacuum, not pressure
• Injectors are available in natural PVDF or ECTFE (NSF-51 and FDA 177.2510 approved
thermoplastics or stainless steel
Read more about Selecting an Injector.
PVDF advantages
• PVDF is an advanced thermoplastic that is superior to other types including PVC, Polypropylene,
& Polyethylene
• Higher pressure and temperature handling capabilities
• Resistant to ozone
• Resistant to Chlorine, Sulfuric and Nitric Acids
• Better abrasion and wear resistance
• Sunlight (UV) resistant

Selecting an Injector
Mazzei® Injectors are of very high quality and are engineered for exact performance. Selecting the
right injector simply requires that you refer to the performance tables found in the resource section
(click here) and follow the guidelines.
• Do want to inject a liquid or a gas
• Injection Rate: How much do you want to inject per hour
• Motive Flow Rate: How much water needs to run through the injector
• Inlet Pressure: What is the water pressure available immediately upstream of the injector
• Outlet Pressure: What pressure will the injector see downstream, after installation
From your answers above, use the Mazzei Injector performance tables to select an injector model able
to exceed your desired injection (suction) rate. The total water flow of the system must be equal to or
greater than the injector's motive flow capacity (water through the injector).
1. Locate the injector inlet pressure on the performance table which most closely corresponds to
your maximum available water pressure.
2. Locate the injector outlet pressure which most closely corresponds to your system pressure
downstream of the injector after installation.
3. Review the performance table to locate an injector model which has a suction capacity that is
greater than your desired suction capacity. Use a metering valve or orifice assembly to adjust
the injector's suction rate to obtain the precise suction required.
Remember, for the injector to operate properly, it must experience a higher inlet pressure than outlet
pressure (called the differential pressure).
There are several installation methods available to ensure the injector operates properly.
NOTES:
Using a metering valve on the suction line can accurately control the suction rate. Viscosity and weight
of material will affect the suction rate.
The water flow (motive flow) listed in the performance tables indicates the amount of water that the
injector must be provided at a given pressure. Since the injector acts as a flow restrictor, this is the
total amount of water that will pass through at this pressure.
The outlet pressure is dependent on restriction to flow in the system downstream of the injector. For
example, if pressurized water is flowing through an injector and runs down a short pipe and simply
falls on the ground, the outlet pressure (back-pressure) is nearly zero. Any restrictions downstream in
the form of piping, filters, valves, sprinklers, emitters, etc. cause the outlet pressure (or backpressure
on the injector) to change.
Should you have any questions, our experienced technical support staff is ready to help. Contact us
with your requirements and allow us to assist you in designing your injection system.

Typical Installation Methods
Fig 1 Fig 2
The injector is installed around a point of restriction such as a regulator valve or a gate/ball valve to
create a differential pressure across the injector. This allows the injector to produce a vacuum and
draw in material. (See Fig.1 and Fig.2)

Fig 3
The injector is installed on the mainline and the pressure reducing device is on the bypass. Chemical
injection can be turned on when the control valve is closed. When the valve is open, injection stops
due to reduced pressure differential. (See Fig.3)

Fig 4
The injector is installed on a bypass with a booster pump. When mainline pressure cannot be reduced,
a small booster pump can be used to create sufficient differential pressure to operate the injector.(See
Fig.4)
Fig 5
The injector is installed in the mainline. The injector must see a sufficient differential to operate. In
other words, the inlet pressure must be sufficiently greater than the outlet pressure.