Calculate the required pump head based on flow rate, pipe dimensions, and static lift.
PVC / Plastic (Smooth) – C=150
Copper – C=140
New Steel / Cast Iron – C=130
Concrete – C=120
Old Iron / Corroded Steel – C=100
Total Dynamic Head (TDH)0.0 ft
Static Head (Elevation)0.0 ft
Friction Head Loss0.0 ft
Fluid Velocity0.0 ft/sec
*Calculations utilize the Hazen-Williams equation for water flow friction loss.
function calculatePumpHead() {
// 1. Get input values
var flowRate = parseFloat(document.getElementById("flowRate").value);
var pipeLength = parseFloat(document.getElementById("pipeLength").value);
var staticHead = parseFloat(document.getElementById("staticHead").value);
var pipeDiameter = parseFloat(document.getElementById("pipeDiameter").value);
var cFactor = parseFloat(document.getElementById("pipeMaterial").value);
// 2. Validation
if (isNaN(flowRate) || isNaN(pipeLength) || isNaN(staticHead) || isNaN(pipeDiameter) || flowRate <= 0 || pipeDiameter <= 0) {
alert("Please enter valid positive numbers for Flow Rate, Length, and Diameter.");
return;
}
// 3. Calculate Friction Head Loss (Hazen-Williams Equation)
// Formula: h_f = 0.2083 * (100/C)^1.852 * (Q^1.852 / d^4.8655) per 100ft
// Where Q is GPM, d is inches.
// Exponents
var qExp = Math.pow(flowRate, 1.852);
var cExp = Math.pow((100 / cFactor), 1.852);
var dExp = Math.pow(pipeDiameter, 4.8655);
// Head loss coefficient per 100 feet
var frictionPer100 = 0.2083 * cExp * (qExp / dExp);
// Total friction loss for the specific length
var totalFrictionHead = frictionPer100 * (pipeLength / 100);
// 4. Calculate Velocity
// V = (0.4085 * Q) / d^2 (Velocity in ft/s, Q in GPM, d in inches)
var velocity = (0.4085 * flowRate) / Math.pow(pipeDiameter, 2);
// 5. Calculate Total Dynamic Head (TDH)
var tdh = staticHead + totalFrictionHead;
// 6. Display Results
document.getElementById("tdhResult").innerText = tdh.toFixed(2) + " ft";
document.getElementById("staticResult").innerText = staticHead.toFixed(2) + " ft";
document.getElementById("frictionResult").innerText = totalFrictionHead.toFixed(2) + " ft";
document.getElementById("velocityResult").innerText = velocity.toFixed(2) + " ft/sec";
// Show the result box
document.getElementById("results").style.display = "block";
}
How to Calculate Pump Head from Flow Rate
Selecting the correct pump for a water system is critical for efficiency and longevity. The two most important factors in pump sizing are the Flow Rate (how much water you need to move) and the Total Dynamic Head (TDH) (how much pressure the pump needs to overcome). This guide explains how to calculate pump head when you know your desired flow rate.
Key Definition:Total Dynamic Head (TDH) is the total equivalent height that a fluid is to be pumped, taking into account friction losses in the pipe. It is usually measured in feet or meters.
The Components of Pump Head
To calculate the pump head required, you cannot simply look at the vertical distance. You must sum up two primary components:
1. Static Head (Elevation)
This is the vertical distance the water must be lifted. It is independent of the flow rate.
Static Suction Lift: Vertical distance from the water source down to the pump (if the water is below the pump).
Static Discharge Head: Vertical distance from the pump up to the final discharge point.
Total Static Head: The total vertical rise from the surface of the water source to the discharge point.
2. Friction Head (Dynamic Loss)
This is where the Flow Rate becomes critical. As water moves through a pipe, it creates friction against the pipe walls. This friction acts as resistance, which the pump must overcome. This resistance is calculated as "equivalent feet of head."
Friction loss is influenced by:
Flow Rate (GPM): Higher flow creates significantly more friction (friction increases exponentially with flow).
Pipe Diameter: Smaller pipes create much higher friction losses than larger pipes.
Pipe Length: Longer pipes result in more cumulative friction.
Pipe Material: Rough materials (like old iron) cause more friction than smooth materials (like PVC).
The Calculation Formula
The simplified formula for Total Dynamic Head is:
TDH = Static Head + Friction Head
Calculating Friction Loss (Hazen-Williams Equation)
While there are several methods to calculate friction, the Hazen-Williams equation is the standard for water systems. Our calculator above uses this method:
Imagine you need to pump water from a well to a tank.
Desired Flow: 20 GPM
Vertical Lift (Static): 30 feet
Pipe Length: 200 feet
Pipe: 1.5-inch PVC
Step 1: Identify Static Head. This is simply 30 feet.
Step 2: Calculate Friction. Using the calculator or friction tables, pushing 20 GPM through 1.5″ PVC creates roughly 3.5 feet of head loss per 100 feet of pipe.
Total Friction: 3.5 ft x (200 ft / 100) = 7 feet.
Step 3: Total Head. 30 ft (Static) + 7 ft (Friction) = 37 feet TDH.
You would then look for a pump curve that can deliver 20 GPM at 37 feet of head.
Why Pipe Diameter Matters
If you increase the flow rate without increasing the pipe diameter, the friction loss skyrockets. For example, doubling the flow rate increases friction loss by nearly 4 times. If your calculated head is too high for standard pumps, the most effective solution is often to increase the pipe diameter, which drastically reduces the friction head component.