Distance from the lowest water level to the top of the well.
Target pressure (usually 40, 50, or 60 PSI).
Water demand (Avg house: 7-12 GPM).
Distance from pump to pressure tank.
Calculation Results
Total Dynamic Head (TDH):
Pressure Head:
Estimated Friction Loss:
Recommended Horsepower (HP):
Understanding Well Pump Sizing
Choosing the right well pump is critical for maintaining consistent water pressure and ensuring the longevity of your plumbing system. A pump that is too small won't provide enough pressure, while one that is too large will cycle on and off frequently, leading to premature motor failure.
What is 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 consists of three main components:
Vertical Lift: The actual vertical distance from the water level in the well to the discharge point.
Pressure Head: The energy required to maintain pressure in your house (1 PSI = 2.31 feet of head).
Friction Loss: The resistance the water encounters as it flows through the pipes, valves, and elbows.
Typical GPM Requirements
When calculating your Gallons Per Minute (GPM) needs, consider the number of fixtures in your home:
🏠 1-2 Bathrooms: 7 – 10 GPM
🏠 3-4 Bathrooms: 10 – 15 GPM
🚜 Irrigation/Large Property: 15+ GPM
Real-World Example
If you have a well where the water sits 100 feet down, you want 50 PSI at the tank, and you have 150 feet of pipe at 10 GPM:
Vertical Lift: 100 ft
Pressure Head: 50 PSI × 2.31 = 115.5 ft
Friction Loss: ~5% of pipe length = 7.5 ft
Total Dynamic Head: 100 + 115.5 + 7.5 = 223 ft
Based on standard pump curves, a 223 ft TDH at 10 GPM would typically require a 3/4 HP or 1 HP submersible pump depending on the specific model's efficiency.
function calculateWellPump() {
var lift = parseFloat(document.getElementById('verticalLift').value);
var psi = parseFloat(document.getElementById('tankPressure').value);
var flow = parseFloat(document.getElementById('flowRate').value);
var pipe = parseFloat(document.getElementById('pipeLength').value);
if (isNaN(lift) || isNaN(psi) || isNaN(flow) || isNaN(pipe)) {
alert('Please enter valid numbers in all fields.');
return;
}
// 1. Calculate Pressure Head (1 PSI = 2.31 Feet of Head)
var pressureHead = psi * 2.31;
// 2. Estimate Friction Loss
// Using a general estimation: approximately 5 feet of loss per 100 feet of pipe for standard 1″ PE pipe at 10GPM
var frictionLoss = (pipe * 0.05);
// 3. Calculate Total Dynamic Head (TDH)
var tdh = lift + pressureHead + frictionLoss;
// 4. Calculate Water Horsepower
// Formula: (GPM * TDH) / 3960
var waterHP = (flow * tdh) / 3960;
// 5. Calculate Brake Horsepower (Assuming 50% efficiency for submersible pumps)
var brakeHP = waterHP / 0.50;
// Determine recommended standard HP sizes
var recommendedHP = "";
if (brakeHP <= 0.5) {
recommendedHP = "1/2 HP";
} else if (brakeHP <= 0.75) {
recommendedHP = "3/4 HP";
} else if (brakeHP <= 1.0) {
recommendedHP = "1 HP";
} else if (brakeHP <= 1.5) {
recommendedHP = "1.5 HP";
} else if (brakeHP <= 2.0) {
recommendedHP = "2 HP";
} else if (brakeHP <= 3.0) {
recommendedHP = "3 HP";
} else {
recommendedHP = "5+ HP (Consult Professional)";
}
// Display Results
document.getElementById('tdhResult').innerText = tdh.toFixed(2) + " Feet";
document.getElementById('pressureHeadResult').innerText = pressureHead.toFixed(2) + " Feet";
document.getElementById('frictionResult').innerText = frictionLoss.toFixed(2) + " Feet";
document.getElementById('hpResult').innerText = recommendedHP;
document.getElementById('resultsArea').style.display = 'block';
}