To choose a Venturi injector, gather the pressure available at the inlet, the pressure that the sector needs to maintain and the desired injection rate. Compare this data with the model table. At installation, the technical team also needs to define filtration, backflow protection and how to measure injection during commissioning.
How the Venturi injector works
The Venturi uses the energy of the water that circulates in the pipe. As the water passes through the narrow section, it gains speed and its pressure drops. Under the operating conditions envisaged for the model, this low pressure region allows liquid to be aspirated from an open reservoir and incorporated into the irrigation water. Embrapa Tropical Agroindústria, Technical Instructions 7
The piece has a simple construction and uses hydraulic energy. The project needs to reserve pressure for its operation and check what reaches the emitters during injection.
What defines suction: inlet pressure and pressure differential
The selection combines four data points that appear in the manufacturer's performance tables.
- Inlet pressure. It is the pressure available with the system in working condition.
- Pressure at the outlet. It depends on the network downstream of the injector.
- Motive flow. It is the water that passes through the Venturi to make it work.
- Injection rate. It is the volume aspirated per unit of time.
See the combination corresponding to the model and units used in the catalog. The Mazzei guide also informs that the gap between reservoir and injector and the properties of the liquid can change the suction capacity in relation to the table. Mazzei Performance Tables Guide
A laboratory test with the Mazzei 1078 showed that suction changed with both differential and supply pressure. The result belongs to the model and the tested conditions, and helps to understand why an isolated percentage of pressure drop is insufficient to select the equipment. Ferreira, Frizzone and Botrel, Scientia Agricola
Pressure loss: the hydraulic cost of the Venturi
When evaluating the head, check the pressure available during fertigation. In an Embrapa study with small systems, the Venturi arrangement without additional pressurization showed the highest pressure loss among the measured points of the head. The assembly with an auxiliary pump had different behavior. These are the results of that installation, which reinforce the need to evaluate the whole. Embrapa Meio-Norte, Technical Notice 276
Take the injector data to the motor pump sizing and check the pressure in the sectors with the injection running. The guide on how to choose the pump for irrigation explains how to consider flow, unevenness and network losses.
Ways to install the Venturi injector
In line (series)
In this arrangement, the line flow passes through the injector. The responsible team must check whether the expected driving flow and output pressure are compatible with the part and the irrigation. The installation needs to be evaluated at the complete work point. Performance data by Mazzei model
By-pass with registration on the main line
The Venturi is in a bypass. A restriction between the take-off and return points can provide the necessary differential. The by-pass also allows the use of an injector whose driving flow is lower than the total sector flow. The adjustment must be defined in the project and checked by pressure gauges, including the pressure that remains available for irrigation. Mazzei, Technical Bulletin 7
By-pass with auxiliary pump (booster)
A booster pump can create the differential when reducing main line pressure would harm the system. Its selection considers the injector operating point, flow rate and bypass losses. The manufacturer presents this arrangement among the possible assemblies. Mazzei, installation methods
The auxiliary pump control must integrate the operating and blocking conditions of the installation. The Mazzei documentation presents interlocking with the main pump in its example of siphoning prevention. This logic needs to be specified and tested by the responsible team. Mazzei, siphoning and backflow prevention
Where the injector enters the control head
The injection position must allow particles of the solution to be retained before they reach the emitters. Embrapa recommends installing it before the screen or disc filter, or providing your own filtration. Check the arrangement for water, products and equipment at the facility. Embrapa Tropical Agroindustry
The Mazzei scheme includes a sieve and dosing valve in the suction. For the models described, the installation sheet guides horizontal body or outlet facing up, appropriate connections and pressure gauges near the inlet and outlet. Follow the manual for the chosen model. Mazzei Installation Notes, 2023 Edition
Source protection needs to be addressed in the design. The suction check valve and the main line backflow preventer have different functions. The manufacturer's documentation provides for protection in the main line and measures against siphoning, including the height of the tank and system shutdown. The team must specify and test these devices under installation conditions. Mazzei, siphoning and backflow prevention
To plan the set, see the irrigation filters and the service of automation and fertigation from Perin.
How to calibrate injection rate in the field
The volumetric rate is the volume aspirated divided by the time. The Embrapa manual describes the measurement as the difference between the initial and final volumes of a container. Use this principle in commissioning conducted by the technical team, after checking the mounting and protections. Embrapa, Melão: production, fertigation chapter, p. 84
- Record the test condition. Identify the sector, the valves in operation, the inlet and outlet pressures and the reservoir level.
- Measure volume and time. On the initial hydraulic check with clean water, record how much was vacuumed at a known interval.
- Calculate the rate. Divide volume by time, using supported units.
- Check the repeat. Repeat the measurement and monitor whether the pressures and tank level have changed.
- Validate the application condition. The team must check the rate for the expected solution and repeat the assessment when the sector, regulation or hydraulic condition changes.
For example, vacuuming 15 liters of water in 10 minutes corresponds to 90 L/h. This calculation illustrates a measurement. The dose and duration of fertigation depend on agronomic recommendations and sector management.
The result with water needs to be compared with the solution conditions. The manufacturer publishes corrections for factors such as density and suction unevenness. Mazzei, Technical Bulletin 1
To organize pre-irrigation, compatibility and flushing of lines, consult the common errors in fertigation.
Weak or no suction: most common causes
Compare readings with model chart before changing installation. The Mazzei bulletin links suction failures to conditions like these.
- Incompatible pressures. Back pressure at the outlet can limit suction.
- Insufficient driving flow. Check the condition of the pump, piping and possible obstructions.
- Suction line blocked. Check hose, sieve and valves according to the equipment procedure.
- Deposits inside. Fouling can reduce performance and require specific maintenance.
Cleaning must follow the manual and compatibility of materials, with isolation and depressurization for the intervention. The team must identify the deposit and define the procedure, including when chemical treatment is necessary. Mazzei, Technical Bulletin 10
See also the precautions in the cleaning drippers with chlorine or acid.
When Venturi is not the best choice
- Variable pressure. Assess whether the rate remains in the required range throughout the application.
- Little pressure available in the sector. Compare the arrangement with auxiliary pump and other forms of injection, considering installation and operation. Embrapa Mid-North
- Frequent sector changes. Compare the need for measurement and adjustment with the control options. The guide to automated irrigation on farm helps gather the data for that choice.
In pivots, it is also necessary to evaluate hydraulic stability and injection control. A study by Santos and Zocoler evaluated Venturi associated with a centrifugal pump on a central pivot. The existence of this studied arrangement shows that the decision depends on the project, without allowing its performance to be extrapolated to any equipment. Santos and Zocoler, Irriga, 2015
FAQ
What pressure differential does the Venturi need?
Consult the model table for inlet pressure, back pressure, motive flow and desired injection rate. Confirm the result with measurements at the installation. Mazzei Performance Guide
Is Venturi suitable for any fertilizer?
Check the solubility, compatibility between products and the resistance of the equipment materials to the expected solution. The agronomic recommendation defines the products and doses. Equipment must be selected for the application condition.
Conclusion
Before choosing the Venturi, gather the head pressures, the sector flow and the necessary injection rate. Take this data to the team that will define the model, assembly and protections. Record commissioning measurements to track operation throughout use.
To evaluate fertigation with the Perin Irrigação team, send the municipality, crop, approximate area and water source via WhatsApp (14) 99824-5219 or by email contato@perinirrigacao.com.br.
Sources consulted
Research carried out on 11/05/2026.
- SANTOS, F. J. de S.; LIMA, R. N. de. Fertigation: injectors. Embrapa Agroindústria Tropical, Technical Instructions 7, 2000. Embrapa publication
- FERREIRA, J. O. P.; FRIZZONE, J. A.; BOTREL, T. A. Performance of a Venturi type fertilizer injector for fertigation purposes. Scientia Agricola, 53(1), 1996. Article in SciELO
- SANTOS, F. J. de S. et al. Fertilizer injectors for use in small irrigation systems. Embrapa Meio-Norte, Technical Communication 276, 2025. Embrapa publication
- MAROUELLI, W. A. et al. Fertigation. In: Melon: production, Fruits of Brazil 33. Embrapa Chapter
- SANTOS, L. da C.; ZOCOLER, J.L. Technical and cost evaluation of the use of a Venturi-type injector associated with a centrifugal pump versus a piston-type pump in chemigation via a central pivot. Irriga, 20(4), 2015. Article in Irriga
- MAZZEI. Guide to Injector Performance Tables. 2020. Table reading guide · Data by model
- MAZZEI. Installation Notes for Mazzei Injectors. 2023. Installation sheet · Installation methods
- MAZZEI. Anti-Siphon & Backflow Prevention Equipment Use. 2014. Manufacturer's guidelines
- MAZZEI. Technical Bulletin 7: Installation in a Bypass Assembly. 2011. Manufacturer's bulletin
- MAZZEI. Technical Bulletin 1: Liquid Suction Capacity Corrections. 2016. Manufacturer's bulletin
- MAZZEI. Technical Bulletin 10: Troubleshooting Mazzei Injectors. 2019. Manufacturer's bulletin
