Mazzei fertilizer injectors are commercial-grade, Venturi injectors with no moving parts to wear out or break down. They work by suction, and can draw liquid fertilizer from virtually any container. The Mazzei can be plumbed on a bypass for less restriction (the preferred method), or directly into a main water line.

It is important to choose the model size carefully based on the water usage of the irrigation system. Select the injector that matches the flow rate (GPH) that your irrigation system uses. An oversized injector will not draw the fertilizer at all; an undersized injector will restrict the flow of the system. If in doubt always choose a smaller size and install on a bypass assembly. This allows you to adjust the Mazzei's flow with less restriction. 

In order for the Mazzei to work properly there has to be a 25% pressure differential between the incoming pressure and the out going pressure, this will make the vacuum effect to draw fertilizer. You will need to experiment to get the dosages required, but once operating, the Mazzei is incredibly reliable and relatively maintenance free.

Find out which fertilizer injector works best for you with the Injector Selector.

    • If taking apart the Mazzei injector for cleaning, be careful not to lose the spring or ball inside the injector. Replacement springs and balls can be purchased if necessary and are included in the Mazzei rebuild kits.

Mazzei Flow Chart (Venturi style)

Mazzei UnitMinimum Flow at 50 PSI InletFertilizer Draw with outlet pressure at
30 PSI (20 PSI Drop)10 PSI (40 PSI Drop)
IM12VLF - 1/2" Very Low (#283) 30 GPH 2 GPH 6 GPH
IM12L - 1/2" Low (#287) 60 GPH 3 GPH 8 GPH
IM12H - 1/2" High (#384) 150 GPH 10 GPH 14 GPH
IM34L - 3/4" Low (#484A) 240 GPH 12 GPH 17 GPH
IM34H - 3/4" High (#584) 425 GPH 21 GPH 25 GPH
IM1L - 1" Low (#878) 750 GPH 56 GPH 75 GPH
IM1 - 1" (#1078) 1050 GPH 86 GPH 92 GPH

Use the chart above to select the Mazzei model according to the gallons per hour (GPH) that your irrigation system uses, not the GPH that you have available from your water source. For example: If you are using 100 x 1 GPH emitters, your system will use 100 GPH. You would need to select the 1/2" Low Flow Injector (IM12L) which requires a minimum of 60 GPH to operate. The next largest injector (IM12H) requires a minimum flow of 150 GPH and is too large for a this system.