Estimate the required pump size for your water system by providing the details below. This helps ensure adequate water pressure and flow.
0.75″
1″
1.25″
1.5″
2″
Understanding Booster Pump Sizing
A booster pump is used to increase the pressure and flow rate of water in a plumbing system. Sizing a booster pump correctly is critical for its performance, efficiency, and lifespan. An undersized pump will fail to deliver the desired pressure, while an oversized pump will waste energy, cause excessive wear, and potentially damage your plumbing through water hammer. This calculator helps you estimate the key metrics needed to select the right pump: Total Dynamic Head (TDH) and the required Horsepower (HP).
Key Factors in Pump Sizing
Several factors contribute to determining the right pump size. Our calculator uses the following inputs:
Total Flow Rate (GPM): This is the total volume of water required per minute. You can estimate this by adding up the GPM ratings of all fixtures that might run simultaneously. For a typical home, 10-20 GPM is a common range.
Required Pressure (PSI): This is the desired water pressure at the highest or farthest fixture in your system. Most residential fixtures operate well between 40-50 PSI.
Vertical Lift / Static Head (Feet): This is the total vertical distance from the pump's location to the highest point where water is delivered. For a two-story house, this might be 20-30 feet.
Pipe Length and Diameter: Water flowing through pipes encounters friction, which results in pressure loss. Longer and narrower pipes create more friction. This calculator estimates this "friction loss" based on your inputs.
How the Calculation Works
The calculator determines the Total Dynamic Head (TDH), which is the total equivalent height that the fluid is to be pumped, taking into account all losses. The formula is:
TDH = Static Head + Pressure Head + Friction Loss
Pressure Head: The energy required to achieve the desired PSI. It's calculated by converting PSI to feet of head (1 PSI = 2.31 feet).
Friction Loss: The head lost due to friction from the pipe walls and fittings. The calculator uses standard friction loss tables for PVC pipe and adds an allowance for fittings.
Once TDH is known, the required Brake Horsepower (BHP) is calculated. This is the actual power needed at the pump shaft. Finally, a standard Motor Horsepower (HP) is recommended, which is the next commercially available motor size up from the calculated BHP.
Example Calculation
Let's consider a scenario for a two-story home:
Flow Rate: The family might use a shower (2.5 GPM), a faucet (1.5 GPM), and a toilet (1.6 GPM) at once. Let's plan for a peak demand of 10 GPM.
Required Pressure: They want a strong shower, so they need 45 PSI at the second-floor bathroom.
Static Head: The pump is in the basement, and the showerhead is 25 feet above it.
Pipe System: The total pipe run is 120 feet of 1-inch diameter pipe.
Using these values, the calculator would determine a TDH of approximately 142 feet and recommend a 0.75 HP or 1 HP motor to reliably meet these demands.
Disclaimer: This calculator provides an estimate for educational purposes. Pipe material, age, water temperature, and the exact number of fittings can all affect the final calculation. Always consult a qualified plumbing professional or pump supplier to verify your requirements before making a purchase.
function calculatePumpSize() {
// Clear previous results and errors
document.getElementById("result").innerHTML = "";
// Get input values
var flowRate = parseFloat(document.getElementById("flowRate").value);
var requiredPressure = parseFloat(document.getElementById("requiredPressure").value);
var staticHead = parseFloat(document.getElementById("staticHead").value);
var pipeLength = parseFloat(document.getElementById("pipeLength").value);
var pipeDiameter = parseFloat(document.getElementById("pipeDiameter").value);
// — Input Validation —
if (isNaN(flowRate) || flowRate <= 0 ||
isNaN(requiredPressure) || requiredPressure <= 0 ||
isNaN(staticHead) || staticHead < 0 ||
isNaN(pipeLength) || pipeLength { Flow Rate (GPM): Loss per 100ft }
0.75: { 5: 5.8, 10: 20.1, 15: 41.5 },
1: { 5: 1.8, 10: 6.3, 15: 13.2, 20: 22.3 },
1.25: { 10: 2.3, 15: 4.8, 20: 8.1, 30: 16.9 },
1.5: { 10: 1.1, 20: 4.0, 30: 8.4, 40: 14.1 },
2: { 20: 1.3, 30: 2.8, 40: 4.7, 50: 7.1, 60: 9.9 }
};
var frictionLossPer100ft = 0;
var diameterTable = frictionLossTable[pipeDiameter];
if (diameterTable) {
var flowRates = Object.keys(diameterTable).map(Number).sort(function(a, b){return a – b;});
if (flowRate = flowRates[flowRates.length – 1]) {
frictionLossPer100ft = diameterTable[flowRates[flowRates.length – 1]];
} else {
// Linear interpolation for values between table points
for (var i = 0; i = flowRates[i] && flowRate <= flowRates[i+1]) {
var x1 = flowRates[i];
var y1 = diameterTable[x1];
var x2 = flowRates[i+1];
var y2 = diameterTable[x2];
frictionLossPer100ft = y1 + ((flowRate – x1) * (y2 – y1)) / (x2 – x1);
break;
}
}
}
} else {
document.getElementById("result").innerHTML = 'Calculation for this pipe diameter is not supported.';
return;
}
// Add ~15% to pipe length to account for fittings (elbows, tees, etc.) as a rule of thumb
var effectivePipeLength = pipeLength * 1.15;
var totalFrictionLoss = (effectivePipeLength / 100) * frictionLossPer100ft;
// 3. Calculate Total Dynamic Head (TDH)
var tdh = staticHead + pressureHead + totalFrictionLoss;
// 4. Calculate Brake Horsepower (BHP)
// BHP = (TDH * GPM * Specific Gravity) / (3960 * Pump Efficiency)
// Assume Specific Gravity of water = 1
// Assume average pump efficiency of 60% (0.60)
var pumpEfficiency = 0.60;
var bhp = (tdh * flowRate) / (3960 * pumpEfficiency);
// 5. Recommend Motor Horsepower (HP)
// Select the next standard motor size up from the calculated BHP.
var standardHP = [0.33, 0.5, 0.75, 1, 1.5, 2, 3, 5];
var recommendedHP = "5+"; // Default for very large requirements
for (var i = 0; i < standardHP.length; i++) {
if (bhp <= standardHP[i]) {
recommendedHP = standardHP[i];
break;
}
}
// — Display Results —
var resultHTML = '
Calculation Results
';
resultHTML += '
Total Dynamic Head (TDH): ' + tdh.toFixed(2) + ' Feet
';
resultHTML += '
Required Brake Horsepower (BHP): ' + bhp.toFixed(3) + ' HP
';
resultHTML += '
Recommended Motor Size: ' + recommendedHP + ' HP
';
resultHTML += 'This is an estimate. Consult a professional for final selection.';
document.getElementById("result").innerHTML = resultHTML;
}