{"id":1262,"date":"2026-09-05T11:30:00","date_gmt":"2026-09-05T03:30:00","guid":{"rendered":"https:\/\/borrapumps.com\/blog\/what-is-head-in-a-pump\/"},"modified":"2026-09-06T01:00:26","modified_gmt":"2026-09-05T17:00:26","slug":"what-is-head-in-a-pump","status":"publish","type":"post","link":"https:\/\/borrapumps.com\/fr\/blog\/what-is-head-in-a-pump\/","title":{"rendered":"What Is Head in a Pump? Pressure, TDH, and Selection Explained"},"content":{"rendered":"

Pump head is the mechanical energy a pump adds to a liquid per unit weight, commonly expressed as metres or feet of that liquid. It is not the physical height of the pump and is not identical to pressure. For an incompressible liquid, pressure rise relates to head through density and gravity, so the same head produces different pressure for liquids with different density. Pump selection uses total dynamic head: elevation, pressure, velocity, and friction effects between defined system points at the required flow.<\/p>\n

This article is a practical diagnostic and procurement guide, not a substitute for the pump manufacturer's instructions, an approved system design, current electrical and plumbing rules, or qualified site service. Isolate energy and pressure before opening equipment. Well work, lifting, confined spaces, wastewater, wet electrical locations, and energized testing require competent personnel and task-specific controls.<\/p>\n

Contents<\/strong><\/p>\n
    \n
  1. Why engineers use head<\/a><\/li>\n
  2. Build total dynamic head<\/a><\/li>\n
  3. Understand static and friction components<\/a><\/li>\n
  4. Use the correct suction level<\/a><\/li>\n
  5. Plot more than one duty point<\/a><\/li>\n
  6. Verify head in the field<\/a><\/li>\n
  7. Decision table<\/a><\/li>\n
  8. Frequently asked questions<\/a><\/li>\n<\/ol>\n<\/div>\n

    Why engineers use head<\/h2>\n

    Head lets a pump curve describe energy addition with less dependence on liquid density than a pressure-only curve. A centrifugal pump generating a given head on water can show a different pressure rise on a denser or lighter liquid, while required power changes with density and efficiency. Always state the liquid, temperature, and units. Do not convert a nameplate pressure into head without knowing where it was measured and whether it is gauge, differential, or absolute pressure. Vapor pressure and suction conditions require their own consistent reference.<\/p>\n

    Build total dynamic head<\/h2>\n
    \"what
    what is head in a pump \u2014 build total dynamic head. BORRAPUMP media library; illustrative context, not a performance claim.<\/figcaption><\/figure>\n

    Choose a suction reference point and a discharge reference point. Account for elevation difference, required pressure difference, velocity-head difference when significant, and friction losses through suction and discharge pipes, fittings, valves, filters, heat exchangers, meters, and nozzles. In an open tank-to-open tank system, both surfaces may be at atmospheric pressure, but elevation and friction remain. In a closed or pressurized system, required destination pressure can dominate. Document the equation and the basis for each term so another reviewer can reproduce it.<\/p>\n

    Understand static and friction components<\/h2>\n

    Static head depends mainly on the elevation and pressure boundary and does not vanish when flow is zero. Friction head rises with flow and depends on inside diameter, length, roughness, viscosity, fittings, and equipment. This creates a system curve. The pump operating point is where that system curve intersects the pump curve at the current speed and impeller. A throttled valve increases resistance and shifts the point; it does not make the pump independently deliver its published maximum flow and maximum head at the same time.<\/p>\n

    Decision table<\/h2>\n
    \n\n\n\n\n\n\n\n\n
    Head component<\/th>\nWhat it represents<\/th>\nTypical input<\/th>\n<\/tr>\n<\/thead>\n
    Elevation head<\/td>\nVertical energy difference<\/td>\nSource and destination elevations<\/td>\n<\/tr>\n
    Pressure head<\/td>\nRequired pressure difference<\/td>\nVessel or terminal pressures and density<\/td>\n<\/tr>\n
    Velocity head<\/td>\nDifference in flow velocity energy<\/td>\nPipe areas and velocity<\/td>\n<\/tr>\n
    Friction head<\/td>\nLosses while liquid flows<\/td>\nPipe, fittings, valves and equipment<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

    Use the correct suction level<\/h2>\n
    \"what
    what is head in a pump \u2014 use the correct suction level. BORRAPUMP media library; illustrative context, not a performance claim.<\/figcaption><\/figure>\n

    For a well, tank, pit, or reservoir, use the operating liquid level for the case being checked. The lowest source level often gives the highest static lift. In a pressurized suction vessel, include that pressure correctly. Suction gauge readings near the pump can support diagnosis but do not replace the full energy balance. Net positive suction head is a related but separate check comparing the absolute suction energy above vapor pressure with the pump's requirement and the project margin. Confusing discharge head with NPSH can lead to cavitation.<\/p>\n

    Plot more than one duty point<\/h2>\n

    Calculate normal, minimum-flow, maximum-flow, lowest source level, highest destination pressure, dirty-filter, alternate pipe route, and parallel-pump cases that can actually occur. Plot them on the certified curve. Check efficiency, absorbed power, motor load, minimum continuous flow, runout, shutoff, vibration, and any preferred operating region. For variable speed, review the full speed and control range rather than one nominal point. A single total dynamic head value can hide an operating envelope that the selected pump cannot safely cover.<\/p>\n

    Verify head in the field<\/h2>\n
    \"what
    what is head in a pump \u2014 verify head in the field. BORRAPUMP media library; illustrative context, not a performance claim.<\/figcaption><\/figure>\n

    At commissioning, measure suction and discharge pressure at known elevations, flow, speed, liquid condition, source and destination levels, and valve positions. Correct gauge readings to consistent reference points and include velocity effects if material. Compare the calculated differential head with the curve and motor input. Calibration, trapped air, pulsation, blocked gauge lines, and poor tap locations can distort results. Preserve the field readings and system configuration so later performance tests use the same basis.<\/p>\n

    System selection, evidence, and procurement record<\/h2>\n

    Evaluate the pump as part of a hydraulic system, not as an isolated motor and impeller. Define the liquid, temperature, gas and solids, source level, required flow range, discharge level or pressure, suction and discharge pipe sizes, fittings, valves, filters, elevation, operating hours, starts, control method, power supply, environment, and standby requirement. Calculate normal and limiting total dynamic head, then plot those cases against a certified curve. Check absorbed power, efficiency, minimum-flow or cooling limits, suction conditions, material compatibility, and the consequences of a blocked or closed path.<\/p>\n

    Use measurements to separate hydraulic, mechanical, electrical, and process causes. A disciplined record can include flow, suction and discharge pressure, source and destination levels, voltage, current, power, speed, vibration, bearing temperature, leakage, sound, runtime, starts, valve position, and liquid condition. Compare like-for-like readings at a stable operating condition. A single symptom rarely proves which component has failed, and replacing parts without establishing the operating point can hide the actual system problem.<\/p>\n

    For procurement and acceptance, define the boundary of supply, duty points, materials, connections, dimensions, driver, controller, protection, instruments, base, guards, lifting, coating, tests, documents, spares, preservation, installation, and commissioning. Resolve deviations before purchase. During startup, verify direction of rotation where applicable, valve lineup, lubrication, alignment, protection settings, leaks, noise, vibration, flow, pressure, current, and alarm response using approved procedures. Preserve the selection sheet, curve, drawings, settings, manuals, test records, and baseline readings for future maintenance.<\/p>\n

    A pillar guide should also be used as a shared calculation and review reference. Define the measurement points, coordinate system, units, liquid properties, normal and limiting cases, instrument accuracy, acceptance tolerance, and responsible reviewer. Keep the calculation assumptions beside the selected curve and revise them when pipe routes, levels, valves, equipment, controls, or operating objectives change. During technical bid review, normalize every supplier offer to the same duty and boundary before comparing efficiency, motor size, price, or delivery. During commissioning, measure the same variables used in the calculation and reconcile any difference before accepting the system. During operation, trend those readings at a repeatable condition so wear, blockage, changed resistance, incorrect valve position, sensor drift, or source variation can be separated. This creates one dependable chain from design through procurement, startup, and maintenance instead of several disconnected estimates. Include the approved drawings, calculation, curve, data sheet, deviations, test records, settings, spare-parts list, and operating limits in the final handover package. A future change should be checked against this baseline rather than judged from a single pressure gauge or subjective observation.<\/p>\n

    Use consistent terminology across the hydraulic calculation, equipment schedule, control narrative, piping drawing, instrument list, and commissioning procedure. State whether each pressure is gauge or absolute, whether each elevation refers to pipe centerline or liquid surface, which inside diameter was used for friction, and what fluid density, viscosity, temperature, and vapor pressure apply. Mark temporary hoses, bypasses, partially open valves, dirty filters, and future connections because they change the system curve. Where several pumps operate in parallel or series, calculate the combined curves and the credible combinations rather than multiplying one pump value. Review shutoff, runout, minimum flow, motor load, suction margin, transient pressure, and failure response. Field instruments should have suitable range, accuracy, location, and calibration evidence. If measured performance differs from the prediction, first verify the test configuration and instruments, then reconcile the pump curve and system curve. Do not change an impeller, speed, valve, setpoint, or motor until the responsible review confirms the effects across every operating case.<\/p>\n

    When teaching or reviewing head, work through one clearly labeled example without turning it into a universal answer. Sketch the source and destination, select datum elevations, mark liquid levels and pressure boundaries, list each pipe segment and fitting, and show the assumed flow. Calculate the static contribution first, then the friction contribution at several flows, and plot the system curve. Add the pump curve for the actual speed and impeller and identify the intersection. Next change one variable at a time\u2014source level, valve resistance, filter condition, destination pressure, parallel operation, or speed\u2014to show why the operating point moves. Finally check power and suction margin and state what cannot be concluded from discharge pressure alone. This method helps readers detect sign errors, mixed units, omitted pressure terms, use of outside rather than inside pipe diameter, and the common mistake of adding a pump's maximum flow to its maximum head. Keep the worked sheet with the project so the result can be updated instead of recreated from memory.<\/p>\n

    How this topic connects to BORRAPUMP equipment<\/h2>\n

    This guide supports early review of what is head in a pump<\/a> applications. It does not assign a final model. Send the liquid, flow range, total head, source and destination levels, solids, duty cycle, power, controls, site conditions, quantity, destination, and required approvals so equipment can be checked against the real service.<\/p>\n

    Related BORRAPUMP engineering guides<\/h2>\n
      \n
    • end suction pumps guide<\/a><\/li>\n
    • booster pump design<\/a><\/li>\n
    • construction dewatering pump sizing<\/a><\/li>\n<\/ul>\n

      Authoritative sources and further learning<\/h2>\n

      U.S. Department of Energy pump systems<\/a>; Hydraulic Institute pump resources<\/a>; NIST SI units<\/a>. These sources provide general engineering, water, environmental, or safety context; current local rules, approved designs, and equipment instructions remain controlling.<\/p>\n