# Irrigation pump: how to choose according to flow rate, head and pump curve Source page: [https://perinirrigacao.com.br/en/blog/bomba-para-irrigacao-como-escolher/](https://perinirrigacao.com.br/en/blog/bomba-para-irrigacao-como-escolher/) Automatically translated from Portuguese. Our projects, service information and technical references relate to Brazil. Contact us to discuss your location and requirements. [Read the Portuguese original](https://perinirrigacao.com.br/blog/bomba-para-irrigacao-como-escolher/) Planning Power in hp is not enough to choose a pump. Understand which project data allows you to compare equipment and evaluate suction and energy consumption. By Team Perin Irrigação Published in October 28, 2026 (2026-10-28) 9 min read ![Drip system in the Perin Irrigação collection](https://perinirrigacao.com.br/assets/perin/responsive/service-drip-640-055633cbf116.webp) Photograph from the Perin Irrigação collection. ## Before you start Irrigation pump: understand flow, head, curves and suction. See what to require in the proposal and follow an example of a hypothetical calculation. **Summary:** Power in hp is not enough to choose a pump. The selection starts with the flow rate and head of the project, goes through the operating point and requires checking suction, performance and equipment limits. Understand what to ask for in the proposal and follow a hypothetical example, without indicating the model or power for a specific property. ## Why the irrigation pump starts with the project, not the catalog A pump works together with the network. Level difference, pipes, filters and emitters determine the operating conditions. The equipment that serves one property may not deliver the flow and pressure needed in another. Before comparing models, the project needs to define which sectors work together, how much water and pressure they require and how this water reaches the pump. The comparison must consider the complete installation, including the most demanding conditions anticipated for the source and filtration. ## The two numbers that define the pump: flow and total head ### Flow: comes from sectorization The project flow corresponds to the sector or set of sectors operating simultaneously. In localized irrigation, the starting point is the number of emitters and their flow under the expected pressure conditions. If backwashing occurs during irrigation, its demand also needs to be included in the assessment. The division into sectors must fit the availability of water and hours of operation. Reducing the instantaneous flow may require more time to serve the entire area. Therefore, area in hectares, alone, does not determine the flow or power of the pump. ### Total manometric height: difference in level, losses and service pressure The total head (AMT or HMT) represents the energy supplied by the pump per unit weight of water, expressed in meters. For a catchment and destination under the usual conditions of an irrigation project, the following are assessed: - **Geometric unevenness:** elevation difference between the water level at the source and the point considered in the critical sector. The highest point is not always the most unfavorable; distance and losses also matter. - **Pipe losses:** vary with flow, length, internal diameter, material and condition of the network. The calculation must state the method and assumptions, without using a simplified relationship as an exact rule for any installation. - **Losses in components:** filters, valves, connections and injectors. The expected loss in [irrigation filters](https://perinirrigacao.com.br/en/conteudos/filtros-de-irrigacao/) it must include the operational condition adopted in the project, including the limit defined for cleaning or backwashing. - **Service pressure:** necessary pressure in emitters and other equipment. No [pressure-compensating dripper](https://perinirrigacao.com.br/en/blog/gotejador-autocompensante/), it is necessary to respect the compensation range, beyond the limits of the network. Suction, pressure and lateral losses must appear in the calculation memory, without omissions or double counting. Pressurized intakes or destinations also require considering their pressure conditions. ## Pump curve x system curve: where the pump will work The manufacturer's curve relates flow and head for a defined rotor and speed configuration. The system curve shows the height required by the installation at different flow rates. The intersection indicates the expected operating point. Check, at this point, the required efficiency, power and NPSH, in addition to the permitted operating range. The best performance point is an important reference, but it does not exempt other limits. The Hydraulic Institute highlights that operating outside of appropriate regions can increase stress, vibration and reliability issues. This helps to understand two situations: 1. **Same power does not mean same performance.** Models with engines of similar power can meet different combinations of flow and head. 2. **A bigger pump does not guarantee a better solution.** Excess may displace operation, increase pressure or require additional controls. Rotor, rotation or sectorization adjustments need to be evaluated with the manufacturer and the person responsible for the project. Each combination of sectors can change the network requirement. A frequency inverter can be part of the solution, but its result depends on the geometric height, curves, yields and usage regime. A theoretical relationship between rotation and power does not promise savings in actual installation. ## Suction and NPSH: a point that often causes problems in the field Cavitation involves the formation and collapse of vapor bubbles in the flow and can damage the pump. Noise or vibration raise suspicion, but they also have other causes and require investigation. O **NPSH available** depends on the installation and water. O **NPSH required** is stated by the manufacturer for the operating condition. The comparison must include the appropriate margin for the equipment and service. Simply equalizing the two numbers, or exceeding by any difference, does not prove cavitation-free operation. Many curves use the NPSH3 criterion, associated with a drop in height in the test, and not with the beginning of all bubble formation. When evaluating suction, the following are included: - **Source level and pump position:** varying the level changes the inlet conditions. - **Suction losses:** piping, fittings, valves and obstructions reduce available load. - **Altitude:** local atmospheric pressure participates in the calculation. - **Water temperature:** modifies the vapor pressure and the available margin. The verification must cover the operating points and the minimum level predicted at the source. In wells, the dynamic level during pumping matters, not just the level observed when the assembly is stopped. ## Power, engine and energy efficiency Hydraulic power, shaft power and electrical power are different quantities. The pump transfers part of the energy received from the engine to the water; the motor also has losses. Comparing proposals requires knowing the performance under working conditions, and not just the nominal power of the board. - **Engine sizing:** it must meet the power required in the expected operating range, the service conditions and the manufacturer's guidelines. - **Efficiency and maintenance:** comparing repair or replacement asks for data on the engine and the service performed. The same performance should not be assumed for every new or repaired engine. - **Energy cost:** depends on consumption in kWh, operating regime and tariff conditions. Benefit rules and schedules may change; confirm current framework and conditions with the distributor before organizing shifts. A [automation](https://perinirrigacao.com.br/en/automacao-fertirrigacao/) This planning must be reconciled with the crop’s water needs. Installation, protection, start-up and electrical changes must be defined and carried out by qualified professionals, according to the equipment and local conditions. ## Hypothetical Example: How Numbers Combine The example below is **hypothetical**. Shows a simplified energy bill and does not select a pump or motor for a property. **Assumptions:** flow of 30 m³/h; 25 m difference in level between the dam surface and the critical emitter; total losses of 13 m, including suction, piping, connections, filter in the expected condition and sides; pressure required in this emitter of 10 m of water column. Losses already included are not added back. - Total pressure head = 25 + 13 + 10 = **48m**. - Converted flow = 30 ÷ 3,600 ≈ **0.00833 m³/s**. - Adopting specific water weight of 9.81 kN/m³, the hydraulic power = 9.81 × 0.00833 × 48 ≈ **3.92 kW**. - With hypothetical efficiency of 65% at the pump and 88% at the motor, electrical power ≈ 3.924 ÷ (0.65 × 0.88) = **6.86 kW**. If the pump's efficiency were 75%, maintaining the same flow, head and engine efficiency, the bill would be approximately **5.95 kW**. It is a comparison between assumptions, not savings measured in the field. The calculated electrical power is also not the rated mechanical power of the motor. There would still be a lack of real curves, verification of suction and NPSH margin, pressure limits and analysis of all sectors. Only this data allows you to complete the selection. ## Checklist to compare pump proposals Check if the proposal states: 1. Design flow and height, with memory of losses and source conditions. 2. Curve corresponding to the proposed rotor and rotation, operating point and efficiency. 3. NPSH available, required and margin adopted in critical conditions. 4. Required power, motor characteristics and definition of the electrical installation. 5. Operating range of all sectors and expected backwash conditions. After installation, flow and pressure measurements and a [uniformity test](https://perinirrigacao.com.br/en/blog/teste-de-uniformidade-gotejamento/) help compare operation with design. An isolated pressure reading does not prove complete performance. ## FAQ ### What is the best pump for irrigation? It is the one that meets the project conditions within an appropriate operating range, with verified performance, motor and suction. The power in hp does not allow us to conclude this alone. ### Which pump to use to irrigate 1 hectare? It depends on the method, the crop, the sectors, the difference in level, the pipes and the source. The area is input data; does not replace hydraulic sizing. ### Can I use the current pump if I expand the area? It may be possible, but the assessment needs to be redone. The new network must be compared to the curves and limits of the set, including in the most demanding suction and operating conditions. ## Conclusion A pump proposal needs to show what the package delivers in the intended installation. Flow, height, curves and suction allow you to compare equipment carefully and identify what still needs to be measured or calculated. Whether you are planning a system or evaluating an extension, the team at [Perin Irrigação](https://perinirrigacao.com.br/en/sistemas-de-irrigacao/) can help organize this analysis. Send municipality, crop, approximate area and water source via WhatsApp [(14) 99824-5219](https://wa.me/5514998245219) or by email contato@perinirrigacao.com.br. ## Sources consulted Original research carried out on 10/27/2026; technical conference and update of references on 10/28/2026. The example is illustrative, with stated premises, and not a pumping project. - [ELETROBRAS/PROCEL. *Practical Manual — Energy Efficiency in Pumping Systems*. 2005. Institutional copy:](https://arquivos.portaldaindustria.com.br/app/conteudo_18/2014/04/22/6281/ManualBombeamento.pdf). - MELLO, C. R.; YANAGI JR., T. *Choosing centrifugal pumps*. UFLA teaching material, made available by USP: [https://sistemas.eel.usp.br/docentes/arquivos/5817712/LOQ4015/escolha bombas.pdf](https://sistemas.eel.usp.br/docentes/arquivos/5817712/LOQ4015/escolha%20bombas.pdf). - [HYDRAULIC INSTITUTE. *The Basics of NPSH & Pump Operating Regions*. 2022.](https://www.pumps.org/2022/12/07/the-basics-of-npsh-pump-operating-regions/) - [GRUNDFOS. *What is an NPSH curve and what is its significance?* Reference on suction margin, without adopting a single margin for all equipment.](https://www.grundfos.com/solutions/support/faq/what-is-an-npsh-curve-and-what-is-its-significance) - [MINISTRY OF MINES AND ENERGY. *Irrigators and aquaculturists will have more flexibility to access discounts on their electricity bills*. 2026. Tariff update reference; Applicable conditions must be confirmed with the distributor.](https://www.gov.br/mme/pt-br/assuntos/noticias/2023-2026/irrigantes-e-aquicultores-terao-mais-flexibilidade-para-acessar-desconto-na-conta-de-luz) ## From knowledge to your project. In agricultural production or green areas, the project starts with the conditions of your area and the water supply. Tell Perin what you need to irrigate. [Request quote](https://perinirrigacao.com.br/en/#contato)[Chat on WhatsApp](https://wa.me/5514998245219?text=Hello%21+I+want+to+talk+about+an+irrigation+project.)