Determine Required Flow Rate, Total Head, and Horsepower
0.75″
1.0″
1.25″
1.5″
2.0″
3.0″
4.0″
Calculation Results
Friction Loss:0
Total Dynamic Head (TDH):0
Hydraulic Horsepower:0
Required Brake HP (BHP):0
Note: This calculation assumes standard smooth pipe friction factors. Real-world conditions and fittings (elbows, valves) will add additional head loss.
Understanding Pump Sizing and TDH
Choosing the correct pump size is critical for the efficiency and longevity of your hydraulic system. Whether you are sizing a well pump, a pool pump, or an industrial transfer pump, you must account for both the volume of fluid moved (Flow Rate) and the resistance it encounters (Head).
1. Flow Rate (GPM)
Gallons Per Minute (GPM) defines how much water you need to move in a specific timeframe. For residential use, this is usually determined by the number of fixtures. For irrigation, it is determined by the nozzle requirements.
2. Total Dynamic Head (TDH)
TDH is the total equivalent height that a fluid is to be pumped, taking into account friction losses in the pipe. It is calculated as:
TDH = Static Head + Friction Loss
Static Head: The vertical distance the water must travel from the source to the discharge point.
Friction Loss: The energy lost as water rubs against the pipe walls. This increases with longer pipes, smaller diameters, and higher flow rates.
3. Pump Horsepower (HP)
Once you know the GPM and TDH, you can calculate the work required. However, no pump is 100% efficient. We calculate Brake Horsepower (BHP) to account for energy lost to heat and friction within the pump itself.
Example Calculation
Suppose you need to pump 40 GPM of water up a 30-foot hill through 200 feet of 2-inch pipe.
Static Head: 30 feet.
Friction Loss: For 200ft of 2″ pipe at 40 GPM, friction loss is approximately 4.5 feet.
TDH: 30 + 4.5 = 34.5 feet.
Brake HP: With a 65% efficient pump, you would need approximately 0.53 HP (typically a 3/4 HP pump would be selected).
function calculatePumpSize() {
// Get Input Values
var flow = parseFloat(document.getElementById("flowRate").value);
var sHead = parseFloat(document.getElementById("staticHead").value);
var length = parseFloat(document.getElementById("pipeLength").value);
var diameter = parseFloat(document.getElementById("pipeDiameter").value);
var eff = parseFloat(document.getElementById("efficiency").value);
var sg = parseFloat(document.getElementById("specGravity").value);
// Validate
if (isNaN(flow) || isNaN(sHead) || isNaN(length) || isNaN(eff) || flow <= 0) {
alert("Please enter valid positive numbers for all fields.");
return;
}
// 1. Friction Loss Calculation (Simplified Hazen-Williams approximation for Water)
// f = 0.2083 * (100/C)^1.85 * (Q^1.85 / d^4.8655)
// Using C=140 for plastic/smooth pipe
var cFactor = 140;
var velocity = (0.408 * flow) / (diameter * diameter);
// Friction head loss per 100ft
var fLossPer100 = 0.2083 * Math.pow((100/cFactor), 1.85) * (Math.pow(flow, 1.85) / Math.pow(diameter, 4.8655));
var totalFrictionLoss = (fLossPer100 * length) / 100;
// 2. Total Dynamic Head
var tdh = sHead + totalFrictionLoss;
// 3. Hydraulic Horsepower (GPM * TDH * SG / 3960)
var hhp = (flow * tdh * sg) / 3960;
// 4. Brake Horsepower (Hydraulic HP / Efficiency)
var bhp = hhp / (eff / 100);
// Display Results
document.getElementById("resFriction").innerHTML = totalFrictionLoss.toFixed(2) + " ft";
document.getElementById("resTDH").innerHTML = tdh.toFixed(2) + " ft";
document.getElementById("resHydraulicHP").innerHTML = hhp.toFixed(3) + " HP";
document.getElementById("resBrakeHP").innerHTML = bhp.toFixed(3) + " HP";
document.getElementById("pumpResult").style.display = "block";
}