Pressure Pipe Flow Rate Calculator

Pressure Pipe Flow Rate Calculator

PVC / Plastic (150) Copper / New Steel (140) Cast Iron / Galvanized (120) Concrete (100) Old Corroded Pipe (80)

Results

Flow Rate (GPM):

0

Flow Rate (LPM):

0

Velocity (ft/s):

0

Head Loss (ft):

0

function calculateFlowRate() { var d = parseFloat(document.getElementById("pipeDiameter").value); var l = parseFloat(document.getElementById("pipeLength").value); var p = parseFloat(document.getElementById("pressureDrop").value); var c = parseFloat(document.getElementById("cFactor").value); if (isNaN(d) || isNaN(l) || isNaN(p) || d <= 0 || l <= 0 || p <= 0) { alert("Please enter valid positive numbers for all fields."); return; } // Head loss (h) in feet of water. 1 PSI = 2.31 feet of water var headLoss = p * 2.31; // Slope (S) = Head Loss / Length var s = headLoss / l; // Diameter (D) from inches to feet var dFeet = d / 12; // Hazen-Williams Formula for Velocity (V in ft/s) // V = 1.318 * C * (R^0.63) * (S^0.54) // Hydraulic Radius (R) for full pipe = D/4 var r = dFeet / 4; var velocity = 1.318 * c * Math.pow(r, 0.63) * Math.pow(s, 0.54); // Flow Rate Q = Area * Velocity var area = (Math.PI * Math.pow(dFeet, 2)) / 4; var flowCFS = area * velocity; // Cubic feet per second // Conversions var flowGPM = flowCFS * 448.831; // 1 CFS = 448.831 GPM var flowLPM = flowGPM * 3.78541; // 1 Gal = 3.78541 Liters document.getElementById("resGPM").innerText = flowGPM.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById("resLPM").innerText = flowLPM.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById("resVelocity").innerText = velocity.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById("resHeadLoss").innerText = headLoss.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById("resultArea").style.display = "block"; }

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Understanding Pressure Pipe Flow Calculation

Calculating the flow rate in a pressurized pipe system is essential for hydraulic engineering, irrigation planning, and industrial plumbing. This calculator utilizes the Hazen-Williams Equation, which is the industry standard for calculating head loss and flow velocity in water systems.

Key Factors in Flow Calculation

• Pipe Diameter: Larger diameters significantly reduce friction and allow for much higher flow rates. Even a small increase in diameter can double the flow capacity.
• Pressure Drop (Head Loss): This is the difference in pressure between two points in the pipe. The higher the pressure drop over a fixed distance, the faster the water will flow.
• Pipe Length: Friction accumulates over distance. The longer the pipe, the more energy (pressure) is lost due to contact with the pipe walls.
• Roughness Coefficient (C-Factor): Different materials have different internal smoothness. PVC is very smooth (C=150), whereas old corroded iron pipes (C=80) create significant resistance.

The Hazen-Williams Formula

The core logic used in this tool is based on the imperial Hazen-Williams formula:

V = 1.318 × C × R^0.63 × S^0.54

Where:

• V: Velocity (ft/s)
• C: Roughness Coefficient
• R: Hydraulic Radius (Diameter/4 for full pipes)
• S: Slope (Head Loss / Pipe Length)

Typical C-Factor Values

Material	C-Factor
PVC / Plastic	150
Copper / Stainless Steel	140
New Cast Iron	120
Galvanized Steel	120
Smooth Concrete	110

Practical Example

Imagine you have a 2-inch PVC pipe that is 500 feet long. If you measure a pressure drop of 10 PSI from the start to the end of the line, what is the flow rate?

1. Convert PSI to Head Loss: 10 PSI × 2.31 = 23.1 feet of head.
2. Calculate Slope: 23.1 / 500 = 0.0462.
3. Apply C-Factor: PVC has a C-factor of 150.
4. Result: Using the calculator, this would yield approximately 82 GPM with a velocity of 8.35 ft/s.

Note: This calculator is intended for water at standard temperatures. For highly viscous fluids or extreme temperatures, the Darcy-Weisbach equation may be more appropriate.