Calculate Pump Head Formula

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Total Dynamic Head (TDH) Calculator

In fluid mechanics and hydraulic engineering, "Pump Head" is a critical metric used to determine the total pressure a pump must generate to move liquid through a system. It represents the height of a column of liquid that the pump could theoretically support against gravity.

TDH = Static Head + Friction Head + Pressure Head

Key Components of the Formula

• Static Head: The net vertical distance the liquid must be lifted. This is the difference in elevation between the source liquid level and the highest point of discharge.
• Friction Head Loss: The resistance the liquid encounters as it flows through pipes, valves, and fittings. It depends on pipe material, length, diameter, and flow rate.
• Pressure Head: The additional pressure required at the discharge point, often needed to operate spray nozzles or pressurized tanks. To convert PSI to feet of head, we use the constant 2.31.

How to Calculate Pump Head Step-by-Step

To use the pump head formula correctly, follow these steps:

1. Measure the Vertical Elevation (Static Head) from the liquid source to the destination.
2. Calculate Friction Loss using the Hazen-Williams or Darcy-Weisbach equations for your specific pipe diameter and flow rate.
3. Identify the Required Pressure at the end of the line. If you need 30 PSI at the nozzle, you must convert this to head.
4. Determine the Specific Gravity of the liquid. Water is typically 1.0. Thicker or lighter fluids will change the head calculation.

Example Calculation

Suppose you are pumping water (SG = 1.0) from a well to a tank 40 feet higher. Your piping calculations show a friction loss of 10 feet, and you need 20 PSI of pressure at the tank inlet.

• Static Head = 40 ft
• Friction Loss = 10 ft
• Pressure Head = 20 PSI × 2.31 / 1.0 = 46.2 ft
• Total Dynamic Head (TDH) = 40 + 10 + 46.2 = 96.2 ft

In this scenario, you would select a pump capable of delivering the required flow rate at a minimum of 96.2 feet of head.

function calculatePumpHead() { var staticHead = parseFloat(document.getElementById('staticHead').value); var frictionLoss = parseFloat(document.getElementById('frictionLoss').value); var dischargePressure = parseFloat(document.getElementById('dischargePressure').value); var specificGravity = parseFloat(document.getElementById('specificGravity').value); if (isNaN(staticHead)) staticHead = 0; if (isNaN(frictionLoss)) frictionLoss = 0; if (isNaN(dischargePressure)) dischargePressure = 0; if (isNaN(specificGravity) || specificGravity <= 0) specificGravity = 1.0; // Pressure Head conversion: Head (ft) = (PSI * 2.31) / Specific Gravity var pressureHead = (dischargePressure * 2.31) / specificGravity; // Total Dynamic Head calculation var tdh = staticHead + frictionLoss + pressureHead; // Display Results document.getElementById('resultArea').style.display = 'block'; document.getElementById('totalHeadResult').innerHTML = tdh.toFixed(2) + ' ft'; var breakdownHtml = 'Calculation Breakdown:' + 'Static Head Contribution: ' + staticHead.toFixed(2) + ' ft' + 'Friction Loss Contribution: ' + frictionLoss.toFixed(2) + ' ft' + 'Pressure Head Contribution (' + dischargePressure.toFixed(1) + ' PSI): ' + pressureHead.toFixed(2) + ' ft'; document.getElementById('headBreakdown').innerHTML = breakdownHtml; }